DRILLING FOR PLACER GOLD



HARRON, RICKARD & MeGONE

SOLE AGENTS
AN FRANCISCO




Work continues in spite of snow



DRILLING FOR
PLACER GOLD



^KEYSTONE,



KEYSTONE DRILLER COMPANY
BEAVER FALLS, PENNA.




A deep hole in the High Sierras, California



CONTENTS

PART I PROSPECTING FOR PLACER GOLD WITH
THE KEYSTONE DRILL

BY WALTER H. GARDNER
Chapter 1 The Advantages of the Keystone Drill Page 11

Keystone drills have confidence of engineers. Wide range of use. Keystone
results given preference. Prospecting with shafts. Open cuts. Small hand-
drills. Keystone drill fits needs of engineer. Incident of Keystone usefulness.
Use of Keystone with operating dredges. Summary of Keystone advantages.

Chapter 2 Proper Drilling Methods Page 20

The crew. The Operator. The Fanner. The Fireman and the Waterbuck.
Four-man crew. Selection of machine. Fuels. Extra equipment. Packing
and shipping. Drive pipe, care and kind. Drive pipe, longer lengths.
Drive pipe, inspection. Moving drill. Setting up drill. Starting the hole.
Use of water. Drilling tight ground. Drilling loose ground. Use of jars.
Pumping. Checking Volume of material pumped. Driving. Finishing
hole. Pulling pipe. Panning. Tin prospecting. Platinum. Fire assays
improper. Precautions to be observed. Frozen ground. Unusual condi-
tions.

Chapter 3 Laying out the Ground and Estimating the

Values Page 44

Survey. What map should show. Plotting drill holes. Exploration with
drill. Laying out holes in stream deposit. "Blanket" deposits. Treatment
of amalgam. Determining fineness of gold. Value of milligiam of gold.
Calculation of cubic contents of drill-hole. Compensation for excessive cores.
Other constants in common use. Constant of .3333. Keystone constant of
.27. Reasons for the Keystone constant. No one constant invariably proper.
Combining value of various holes. Principle of evaluation. Calculation when
holes are spaced equidistantly. Other methods. "High Holes". Calculation
of stream channel values. Summary of calculation methods. What report
should cover.

Chapter 4 Reliability of Keystone Samplings Page 65

Keystone estimates now checked. Agreement on Oregon property. Check
on a California property. Another check from large acreage. Check from
small dredge operations. Example from operations of Natomas Cons, of Cali-
fornia. Montana property. Tabulation of available comparisons. Ac-
curate prospecting possible. How different conditions affect accuracy. Sum-
mary. Conclusion. Keystone creek placers. Plates "B", "C", "D", "E",
-F", "G", "H", "I", "J". Field log.

PART II AUTHORITATIVE ARTICLES ON
MINERAL PROSPECTING

The Prospecting and Valuing of Dredging Ground Page 88

by Norman C. Stines.

Laying off the ground. Operation of drilling the hole. Treatment of material
from the hole. The log book. Tables "1", "2". Calculating values. Final
calculations. Value of tests. Accuracy of the tests.



562."



CONTENTS Continued

Prospecting for Copper with Churn Drills Page 111

by F. S. Pheby.

Blasting Tight Placers Before Dredging Page 117

by Oliver B. Finn.

PART III MINERAL PROSPECTING MACHINERY
Mineral Prospecting Machinery Page 124

by R. M. Downie.

Core drills. Things which cannot be done' with a revolving core drill. What

cannot be done with Keystone drills.

Directions for the Operation of Keystone Machines and Use
of Accompanying Appliances Page 135

by R. M. Downie.

Moving and setting up. To string the drilling tools. Keystone cut drive
pipe. The drive pipe. Exploring from a float or flat boat. Driving the pipe.
Dressing the drilling bits. Caution. Pulling the pipe. Pipe pulling ring.

The Science of Zinc and Lead Prospecting with the Churn
Drill Page 171

by R. M. Downie.

Two Prime Requisites in a Prospecting Drill: Page 173

A Long Quick Stroke. A Vacuum Sludge Pump.

Quick stroke how obtained. Tendency of drillings to settle on bottom.
Trituration of drillings by slow motion drills. How to prevent drillings from
settling on the bottom. Keystone drill travel 360 feet per minute. A sim-
ple experiment. Another simple test. An incidental advantage of this
quick stroke. The suction sludge bucket. Still another test. False assays
caused by imperfectly cleaning out the hole. Keystone vacuum sand or sludge
pump. Examination of the sludge.

Drilling Costs in Potash Prospecting Page 183

by E. E. Free.

Cost of data of prospect drilling.

Successful Salting of Alluvials Page 188

by C. S. Haley.

Preliminary examination of alluvials. An unsuccessful attempt. Keystone

and Empire drilling. Drill sampling. Field log. Record of formation.



PAT i

PLACER



PROSPECTING
FOR PLACER GOLD WITH

THE
KEYSTONE DRILL

^^^^ T3ADE HACK. ^^H

.KEYSTONE,



COMPILED BY

WALTER H. GARDNER

And after being critically reviewed by the original designer
of this process and compared with the findings of a wide
circle of authentic and practical engineers who have used
the process, it is

PUBLISHED BY

KEYSTONE DRILLER COMPANY

Beaver Falls, Pennsylvania



DEDICATION

This Manual of Information for the Placer
Engineer is dedicated to the hardy men who have
carried the Keystone to the edges of the world;
who have cleared a path for it with machete
through the matted jungles; who have forgotten
frost-bitten fingers in Alaskan Tundras to finish
"one more hole"; who have lived and toiled in
far lands and outlying camps that they might
reveal new sources of treasure and open new
fields of human endeavor.



PREFACE



"The chum drill is, however, rtie besfr device, gnownfor prp*pe^tinR
ground having the necessary condition* Sot gQld dredging.-.'./. .-. J ,?. t .-

Engineering and Mining Journal

The Keystone Drill, as universally used, is not an instru-
ment of precision. Gold particles are not distributed with
mathematical symmetry. One drill hole to an acre in
ground that is 50 feet in depth only yields for examination
Hw.ooo part of the whole! Ordinary common sense and care
on the part of the operator and panner are sufficient to insure
acceptable field work. Meticulous precision or elaborate
core measurements are generally absurd.

For after the depths have been recorded and the gold
weighed, there comes the calculation of the values of
precious metal in great blocks of gravel. There is no fixed
formula. The experienced Engineer, to whom such work
should be entrusted, will compensate for high variations, for
loose and swelling ground, for sand and clay, for rusty gold
and his calculations will of necessity contain approxima-
tions that eclipse minor errors of the field and nullify minute
measurements .

Indeed, field work with the Keystone Drill need not be
conducted by men of profound skill. Just so the work is
done in a consistent manner under the occasional eye of a
competent engineer; just so the results are interpreted in
the light of experience then will the final figures carry the
full weight of authority.

There is no mystery about field work and should there
be, the following pages will clarify the mode of procedure.



10 DRILLING FOR PLACER GOLD

But there can be no standard of practice in interpreting the
drill rettjrnst-thi&bcto^jcan here only serve as a manual of
suggestions 1 and reminders "to the experienced engineer.

And, &rei -is herein CQn:gaine.cl a review of a generation of
Keystone* use in the light of the actual recovery from subse-
quent mining operations. Hitherto unpublished tables are
offered for the files of all interested in the exploration for
placer gold.

May you find this little book worthy of preservation !

THE AUTHOR.



CHAPTER I

THE ADVANTAGES OF THE
KEYSTONE DRILL

KEYSTONE DRILLS HAVE CONFIDENCE
OF ENGINEERS

To " Keystone" a gold dredging field is to "prospect" it!
So closely has the Keystone Drill identified itself with the
examination and calibration of auriferous gravels that its
very name has grown into the jargon of the Engineer as a
synonym of thorough and conscientious exploration. For
the past twenty-five years have seen extensive areas of river
gravels accepted for exploitation or cast into the discard on
the strength of no other information than that revealed by
the Keystone Drill in competent hands. With a serene con-
fidence in its reliability, men have invested hundreds of thou-
sands of dollars in the purchase of land and dredge machin-
ery or accepted an unfavorable verdict without a question.

WIDE RANGE OF USE

The Keystone Drill was first used for the determination
of gold values in a placer deposit in Idaho, in the spring of
1898. Since that time many hundreds of drills have been
shipped to all parts of the world and used in the testing of
bench and bottom land ; of old channels ; of the bars of live
streams; of lake and river bed. It has clattered in the
depths of the Columbian jungles where it paved the way for
the Nechi and Pato dredges ; it has probed the frozen gravels

11



12 DRILLING FOR PLACER GOLD




The Canadian Klondyke Mining Company used KEYSTONE DRILLS in their
extensive exploration work



DRILLING FOR PLACER GOLD 13

of Alaska and Siberia ; it has charted the wide areas of the
Oroville, Yuba and Natoma districts of California; it has
explored innumerable of the lesser streams of Oregon and
Montana, of the Philippines and the Malay States. It has
sought for gold; for platinum; for diamonds and for tin.
It has been transported under its own power; by horses;
on the backs of mules ; on snow-sleds ; in crude dug-outs
even on the backs of human carriers. Sometimes a half
dozen machines have been purchased and used to hasten the
work on a promising property there were at one time more
than 40 Keystone Drills operating simultaneously on the prop-
erty of the Lenskoi Mines. It has been used to determine the
presence or absence of precious metals ; it has been used to
carefully appraise the contents of whole tracts; it has lo-
cated limits of dredging possibilities both as to values,
depths and bedrock reefs. It has proved that its results are
the best index to dredging possibilities. And it has estab-
lished a reputation for sturdiness and reliability that few
machines enjoy.

KEYSTONE RESULTS GIVEN PREFERENCE

The Engineer who faces the task of correctly determining
the recoverable gold content of a placer field will ordinarily
have several alternatives of procedure. He may put down
shafts. Open cuts or exposed walls may give access to the
various strata. Ke may depend on a small and flimsy
"hand-drill." Or he may elect to do a thorough and ac-
curate exploration with a Keystone Drill. We briefly re-
view the various shortcomings and advantages of these
methods:



14 DRILLING FOR PLACER GOLD

PROSPECTING WITH SHAFTS

Sub-surface waters usually prevent extending a shaft to
bedrock. Uneven and improperly completed shafts do not
yield reliable data. The same inaccuracy attends the at-
tempt to sink a shaft below water level by the use of pumps
or other appliances. The inflow of water will carry values.
To be sure, if water did not interfere, a property might be
thoroughly prospected by shafts and by shafts alone but at
an unnecessarily high cost. And while the final data would
of course be accurate, it would, despite the greater size of
the samples, be little more authoritative than the Keystone
evaluations. So the Keystone Drill holes, miniature shafts
as they are, are today recognized as preferable from the
standpoint of the time and money that they save and as
accurate to nearly the same degree. But the careful Engi-
neer will usually check the operations of his Keystone with
one or more shafts to bedrock if possible and at least to
water-level. He sinks the shaft around one of the early
drill-holes. It gives him a better visualization of the strata
that the drill has already indicated it yields sufficient gold
to obtain a test as to the nature and purity of the particles
it supplies some data for the decision as to the proper "con-
stant" to be employed in his later calculations. And it also
more surely indicates the exact level of the sub -surface
water; it reveals something of the configuration of the bed-
rock; it more clearly tells of clay streaks and buried bould-
ers. But the experienced Engineer will rarely waste time
and energy on more than one such check shaft.

OPEN CUTS

A thorough exploration of a placer field will often dis-



DRILLING FOR PLACER GOLD 15

cover open cuts, old shafts, exposed banks and other oppor-
tunities to cross-cut the gravels to some depth. But such
exploration can seldom be more than casual and is either
merely supplementary or in advance of the determination
to drill thoroughly. For the random nature of such oppor-
tunities does not permit the systematic operations that alone
carry the assurance of accuracy.

SMALL HAND-DRILLS

Standard equipment for use with the Keystone Drill is
Extra Heavy Pipe 6 inches in diameter. It is generally held
that a smaller sample cannot be error-free. Two and a
quarter times as much material is recovered for examination
from the Keystone Drill holes as from a 4-inch pipe. While
there have been cases where the exigencies of transportation
seemed to encourage the lighter machine, and while it may
be permissable for preliminary work, it is of record that few
dredges have been purchased without adequate Keystone
results as the basis for the confidence of the investors. In-
deed, it has become almost an axiom that capital will not be
attracted to a placer field unless it has been thoroughly
"Keystoned"! Nor can the "hand-drill" cope with condi-
tions of hard ground. Dredge operators say that they can
work any gravel that can be broken by a man with a pick
and the operations at Natoma, California, certainly prove
the truth of this contention. But it requires a sturdy ma-
chine to probe such compact gravels heavy enough to
scorn the boulders that are inevitably encountered. The
Keystone Drill is of as light a design as may be confidently
entrusted to test with truth and accuracy the average de-
posit of auriferous or value bearing gravels.



16 DRILLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 17



KEYSTONE DRILL FITS NEEDS OF ENGINEER

The Engineer who wishes his work to carry the full flavor
of accuracy or the promoter or property owner who wishes
to collect data that will command the respect and belief of
others will not be satisfied with any but Keystone Drill re-
turns. Nor is the Keystone so heavy as to be difficult to
transport or to operate. Quite the contrary. The Key-
stone No. 1, with the boiler sectionalized, may be trans-
ported by pack-train. The Keystone No. 3, the standard
model for placer prospecting, is designed for speedy moving
and "setting up"; for the rapid drilling of holes that are but
rarely more than 60 feet in depth ; for hard work far afield
from machine-shop and organized repair facilities in short,
for the peculiar and arduous work of the pioneer Placer
Engineer!

INCIDENT OF KEYSTONE USEFULNESS

There is on record an example of the untrustworthiness of
shafts when they do not go to bedrock. One property was
once prospected to the depth of about ten feet when water
was encountered. These shafts revealed promising values
which had only to be maintained to a reasonable depth to
make an attractive dredging proposition. Indeed, so gratify-
ing were the returns that a company was formed and stock
sold. But cautious capital wisely demanded that the ground
be Keystoned and it was discovered that the lower gravels
were absolutely barren ! It seemed that an old and filled-up
lake bed, or settling basin, had been covered in recent times
with an all too thin layer of auriferous gravel. Here the
Keystone saved a very considerable sum of money for some
one ! Most Engineers prefer, if conditions at all permit, to



18 DRILLING FOR PLACER GOLD

rely on a Keystone even for preliminary work. It is dis-
concerting to arrive at a property after a long trip with noth-
ing more adequate than a "hand-drill" for equipment and
find ground that is too hard for it to attack and containing
too much water for shaft sinking !

USE OF KEYSTONE WITH OPERATING DREDGES

There is yet another angle to the situation. In the event
that preliminary work prompts a complete campaign of
evaluation, the Keystone is absolutely necessary. And when
the dredge is finally completed and at work, the Keystone
has not outlived its usefulness. Modern practice suggests
the continued use of the drill in front of the dredge, blasting
hard ground, determining the boundaries of barren areas,
charting the "pay-streak", seeking out reefs of hard bedrock,
tracing the sub-surface bench line, even forecasting the cur-
rent dredge returns. A large dredging company now follow
this practice, for, as they say, "There is nothing more foolish
or expensive than to prospect with a dredge!"

SUMMARY OF KEYSTONE ADVANTAGES

Here, then, are many reasons why a property under ex-
amination for its gold content should be Keystoned at as
early a date as may be possible

1. Keystone Drills are not too heavy to transport to
properties that are at all accessible.

2. Keystone Drills are able to cope with severe conditions
of deep bedrock, boulders and hard or frozen gravels.

3. Keystone Drills achieve very nearly the accuracy of
shaft work at the cost of less money and time.



DRILLING FOR PLACER GOLD 19

4. Keystone Drill returns command confidence and re-
spect. Their use adds weight to any report on a placer
property.

5. Keystone Drills are practically certain to be specified
on the final examination it is a matter of economy and
efficiency to use them even for preliminary work.

6. Keystone Drills do not outlive their usefulness with
the passing of the period of exploration.



CHAPTER II
PROPER DRILLING METHODS

THE GREW

Efficient operation of the Keystone Drill will in most cases
require a crew of three men the drill-operator, the panner
and a fireman. Usually a man with a team is necessary to
bring water and fuel as well as to aid in moving. Sometimes
the Engineer in charge will prefer to perform most of the
duties of a panner; sometimes, with oil-burning equipment,
one man may be eliminated.

THE OPERATOR

The man who actually runs the drill should be expe-
rienced. On him largely depends the accuracy and certainly
the expedition of the work. He should be capable of the re-
pair, replacement and bit-sharpening which must all be
sometimes conducted under the difficulties of limited con-
veniences afar from shop and machine equipment. The
Engineer will largely be occupied with exploration, survey-
ing, securing supplies, correspondence and manifold duties
his drill-operator should be a dependable lieutenant and a
resourceful mechanic.

THE PANNER

The panner, also, should be an experienced, discreet and
trustworthy man. His duties are to keep the records, check
the core, collect the recovered gravels and slimes, clean up
the sluice-box and make a full report to his superior on all
drilling operations. He is often asked to supplement the

20



DRILLING FOR PLACER GOLD 21

operator's pipe and rope measurements with an independent
check of his own. But the ideal man will do more than that
he will turn a willing hand to whatever chore presents it-
self, for he will have unoccupied moments. It is of impor-
tance that he be provided with shade in hot weather and
shelter and warmth in cold; otherwise his work can not be
kept free from variables incidental to cold and discomfort
and can not be prosecuted with full accuracy it being
unavoidable that his hands be in water much of the time.

THE FIREMAN AND THE WATER-BUCK

The work of keeping up steam and driving the team may
be entrusted to such labor as can be secured in the field of
operations. Ordinarily such men need not be skilled to any
degree but the very nature of prospecting work suggests
that there be some assurance of the loyalty and discretion of
every employee. The fireman should be required to start
his work on each shift in such season that a full head of steam
will be available upon the arrival of the rest of the crew.

FOUR-MAN GREW

In the extensive operations of one large company, the em-
ployment of a fourth man has been found a justifiable ex-
pense. With such a crew it becomes the duty of the fireman
to care for the fuel, water and lubrication; to act as mechan-
ical inspector, keeping all bolts tight ; and to keep a full head
of steam. The fourth man, or "helper", acts as assistant to
both panner and operator ; cleans casing threads ; prepares
roads in advance of moving ; runs needful errands, and in
general serves to keep lost time at a minimum.



22 D R I L L I NG FOR PLACER GOLD




DRILLING FOR PLACER GOLD 23

SELECTION OF MACHINE

For these many years the Keystone No. 3 Traction has
been the favored Model for placer prospecting. It is amply
powerful for all depths and all gravels likely to be encount-
ered. The friction-hoist is to be preferred. The No. 3
Non-Traction may be used, of course, but the traction ma-
chine soon earns back in saved time its somewhat greater
cost. Where transportation into regions difficult of access
must be provided, the lighter Keystone No. 1, with its boiler
sectionalized, may be carried in by pack-train. On those
rare occasions when the holes run beyond 300 feet in depth,
the Keystone No. 5 is specified.

FUELS

The standard fire-box of the Keystone Drill will take wood
of about 18 inches in length by 6 to 8 inches in thickness.
Seasoned wood is the best, of course, but a clever fireman can
keep up steam with damp and green fuel that would appear
almost useless. It is often possible, and always desirable,
that supplies of wood fuel be prepared in advance. Coal
may be used interchangeably with wood, the Keystone grate
being suited to either, but a supply of extra grates is advisa-
ble if coal is to be burned. The machine can easily be
equipped with an oil-burner where proper fuel is secur-
able and when so fitted the costs of operation are mate-
rially lowered. In many parts of Alaska, Keystone Drills
fitted with gasoline engines serve best. The drill will use a
little less than half a cord of wood to a ten-hour shift if
the wood be of average worth, and the operations require
four to six barrels of water.



24 DRILLING FOR PLACER GOLD

EXTRA EQUIPMENT

There are listed hereafter not only the standard equip-
ment for placer testing, but also a selected list of extras and
spares, with the accessories, that intimate acquaintance with
field conditions prescibe as proper and necessary adjuncts to
speedy and efficient work. Let it be borne in mind that the
search for gold is carried on in the far places of the world,
and that, except in those few instances where operations are
amid the conveniences of civilization, placer prospecting
parties must rely largely on their own resources. Indeed, it
is the ruggedness of the Keystone Drill and the simplicity
of its upkeep that have raised it so high in favor! Again,
speed in carrying out the work is invariably to be desired;
there is always an overhead expense in maintaining the crew
that counts heavily in the event of lost time. The simple
precaution of carrying a complete outfit and ample replace-
ment parts will insure against excessive expense and irksome
delay. The drill-bits must be sharpened in the field that
must be provided for. Sand pump valve packings wear out
even an extra valve assembly should be carried as precau-
tion against embarrassment due to breakage. Continued
use eventually * 'fatigues" the bolts for the driving clamps.
Connecting-rod brasses require replacement there are
many possible mischances of minor nature incidental to the
strenuous work of drilling into impacted gravels. It will be
found that the Keystone list of extras as appended cannot be
safely curtailed if there is to be provision against ordinary
hazards; and, indeed, it may well be increased if the expe-
dition is likely to work for a long time far from the beaten
track. A complete set of carpenter and blacksmith tools
will then be found a worthy addition.



DRILLING FOR PLACER GOLD 25

PACKING AND SHIPPING

For domestic use the Keystone Drill will generally be
shipped completely assembled. For use abroad or in dis-
tant fields it may be partially dis-assembled and crated.
The new machine, ordered from the branch of the Keystone
Driller Company, will be carefully inspected to insure imme-
diate readiness for operation. A machine once used, that is to
be transported to a new field of work, should be carefully and
thoroughly looked over by the Engineer so that possible delay
or confusion at time of delivery may be obviated. The
machinery and tools should be checked as complete and in
perfect working order. Packages and crates should be num-
bered and listed to permit of ready identification. All
should be plentifully greased to prevent oxidation in transit.
The rope should be protected from moisture. Steam en-
gine oil and greases should be included in the shipment if
there is any uncertainty as to the availability of these in the
field. Four 3" by 12" planks are often shipped with the
drill, and prove useful in unloading, moving and blocking.
The sluice-box can be made in the field if a piece of 30" by
60" Galvanized Iron, 20 Gauge, be rolled up and included.
The rocker had best be fabricated on the ground from the
best available soft pine for it is almost sure to be dried out
or broken in transportation. Wise forethought will yield
large dividends in saved time and lowered cost of work !

DRIVE PIPE CARE AND KIND

The pipe recommended for placer testing is the Extra
Heavy Drive Pipe (28 pounds to the foot), for the lengths
are driven and pulled and used over again many times. A
generous supply is most desirable on far expeditions three



26 DRILL ING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 27

times as much as would be required for one average hole may
well be purchased and transported. Short lengths are ad-
vised for greater ease in handling an accepted length is
about six feet for each piece, though the first joint may well
be seven or eight feet. The threading must be accurate and
true ; that there be no waste of time in screwing and un-
screwing ; that the joints will butt in the middle of the coup-
ling, thus avoiding danger of thread -stripping, and so that
all pieces will be interchangeable. Threaded ends should at
all times be protected by couplings or short sleeves. Pipe
ordered from the Keystone Driller Company is threaded to
the "Keystone Standard Cut."

DRIVE PIPE LONGER LENGTHS

However, if the holes are to be more than 60 feet in depth,
longer lengths are advisable. To permit their use, provided
that the ground is dry, the hole is started in a pit about 6 feet
in depth and 5 feet by 7 feet in width and length. This pit
is cribbed lightly at the top to prevent the jar of the opera-
tion of the machine from breaking it down; it is covered
with substantial planks and the weight of the drill is sup-
ported on wide and heavy boards. With such a pit 10-foot
lengths may be comfortably used. In wet ground where
timber is plentiful the drill is often cribbed up so as to be
4 to 6 feet above the surface and the same lengths may be
employed. There are then fewer joints to provide the pos-
sible cause of a "crooked hole" when the gravel is compact,
and less time is taken up in making pipe connections.

DRIVE PIPE INSPECTION

In the field it is customary to use certain pieces of pipe in
a regular sequence, numbering them for identification. It



30 DRILLING FOR PLACER GOLD

be taken to examine the material removed for possible val-
ues, although the hole will usually be started in barren silt or
loam. The stem is then lowered into the pipe and the driv-
ing-blocks bolted on. The attendant, mounted on one of
the cross-pieces of the derrick, will steady and balance the
otherwise unsupported stem, while the panner will hold the
pipe until driven to a depth where it can support itself. Or-
dinarily, in surface soil the first drive may be for two feet,
when the depth and core should be read off and recorded.
A little water may then be added (not too much, on account
of the possibility of its washing down through the loose soil)
and a pumping made without drilling. In hard compact
gravel it is sometimes necessary to drill first but this is a
procedure to be avoided if it is at all possible.

USE OF WATER

The contents of the pipe should be kept thoroughly mixed
with water as the work progresses. In dry ground no more
should be added than is necessary perhaps three or four
feet of it in the pipe. But in wet ground the water-
level should be kept above the water-level outside the
casing. This higher head has been found to be efficacious
in largely preventing the inrush of too great a core and the
intrusion of extraneous values. The Engineer will some-
times find this to be a troublesome point, but one that must
be insisted upon. The operator should continually have be-
fore him the fact that he is not there to make progress, but to
gain a correct sample! Care must also be taken to flood the
drill-stem with a bucket of clean water as it comes up after
the drilling and before the pumping, and to give the sand-
pump a final flush on the conclusion of each pumping. The



DRILLING FOR PLACER GOLD 31

boiler water should be kept in a separate barrel where no
dirty buckets are plunged into it. The water used in the
drill hole should be absolutely free from oil or grease of any

kind.

DRILLING TIGHT GROUND

The pipe will have been carefully measured and marked at
intervals of 6 inches with a water-proof crayon. The
assembled drilling tools will also have been measured and
marked so that at any instant the operator will know the
exact relation of the edge of the bit, at the limit of its down-
ward stroke, to the bottom of the cutting-shoe. Drilling
will proceed until the bit is from 1 to 4 inches above the
lower end of the cutting-shoe; this thickness of impacted
gravel prevents the intrusion of too much material from
without the path of the pipe. This thickness of gravel is
alluded to as the "core". The drill-stem should be turned
slightly by the hand of the operator to keep the blade from
striking in exactly the same place and packing the contents
of the pipe or becoming stuck. If a boulder is encountered
it may be broken up by drilling ahead of the pipe proper
notation being made in the log. Drilling below the pipe is
always a bad and a dangerous practice in placer testing, ex-
cept that in heavy ground or coarse gravel it may be neces-
sary to drill a few inches ahead after pumping to clear the
pipe of a plugged core. Before resorting to this expedient,
it should be ascertained that the water-level in the pipe is
above the water-plane in the ground. Fortunately, in such
heavy, tight gravel there is ordinarily found a stiff clay
which serves to protect the walls of the hole below the drive-
shoe.



30 DRILLING FOR PLACER GOLD

be taken to examine the material removed for possible val-
ues, although the hole will usually be started in barren silt or
loam. The stem is then lowered into the pipe and the driv-
ing-blocks bolted on. The attendant, mounted on one of
the cross-pieces of the derrick, will steady and balance the
otherwise unsupported stem, while the panner will hold the
pipe until driven to a depth where it can support itself. Or-
dinarily, in surface soil the first drive may be for two feet,
when the depth and core should be read off and recorded.
A little water may then be added (not too much, on account
of the possibility of its washing down through the loose soil)
and a pumping made without drilling. In hard compact
gravel it is sometimes necessary to drill first but this is a
procedure to be avoided if it is at all possible.

USE OF WATER

The contents of the pipe should be kept thoroughly mixed
with water as the work progresses. In dry ground no more
should be added than is necessary perhaps three or four
feet of it in the pipe. But in wet ground the water-
level should be kept above the water-level outside the
casing. This higher head has been found to be efficacious
in largely preventing the inrush of too great a core and the
intrusion of extraneous values. The Engineer will some-
times find this to be a troublesome point, but one that must
be insisted upon. The operator should continually have be-
fore him the fact that he is not there to make progress, but to
gain a correc t sample! Care must also be taken to flood the
drill -stem with a bucket of clean water as it comes up after
the drilling and before the pumping, and to give the sand-
pump a final flush on the conclusion of each pumping. The



DRILLING FOR PLACER GOLD 31

boiler water should be kept in a separate barrel where no
dirty buckets are plunged into it. The water used in the
drill hole should be absolutely free from oil or grease of any

kind.

DRILLING TIGHT GROUND

The pipe will have been carefully measured and marked at
intervals of 6 inches with a water-proof crayon. The
assembled drilling tools will also have been measured and
marked so that at any instant the operator will know the
exact relation of the edge of the bit, at the limit of its down-
ward stroke, to the bottom of the cutting-shoe. Drilling
will proceed until the bit is from 1 to 4 inches above the
lower end of the cutting-shoe; this thickness of impacted
gravel prevents the intrusion of too much material from
without the path of the pipe. This thickness of gravel is
alluded to as the "core". The drill-stem should be turned
slightly by the hand of the operator to keep the blade from
striking in exactly the same place and packing the contents
of the pipe or becoming stuck. If a boulder is encountered
it may be broken up by drilling ahead of the pipe proper
notation being made in the log. Drilling below the pipe is
always a bad and a dangerous practice in placer testing, ex-
cept that in heavy ground or coarse gravel it may be neces-
sary to drill a few inches ahead after pumping to clear the
pipe of a plugged core. Before resorting to this expedient,
it should be ascertained that the water-level in the pipe is
above the water-plane in the ground. Fortunately, in such
heavy, tight gravel there is ordinarily found a stiff clay
which serves to protect the walls of the hole below the drive-
shoe.



DRILLING FOR P LACER GOLD




Drilling in China behind the protection of a fence and barricade



DRILLING FOR PLACER GOLD 33

DRILLING LOOSE GROUND

If there is loose and running ground there may be but
little drilling necessary, and the utmost skill and experience
of the operator will be called into play to prevent the pump-
ing of too much material. In fact, there will frequently
occur a stratum where the amount of silt and sand pumped
out of the hole will be greater than the theoretical displace-
ment of the drive-shoe a careful recording of volumes will
then give the Engineer data for the approximations and
allowances that must be made. Fortunately, such loose
material seldom contains heavy enrichment. If too thick
a core is maintained, there is a possibility of its becoming a
plug in the pipe and crowding other material aside as it is
driven. The whole science of accurate drilling consists in
pumping as nearly as possible the entire material in the path
of the pipe and no more! No two pieces of ground will
react to drill operations in just the same way; indeed, data
have been collected which show that no two skilled operators
will secure exactly parallel results in the same hole! Here,
as elsewhere, crops up the personal factor which the Engi-
neer will study and reflect in his final calculations. In most
work, however, variations will be so slight as to be ignored,
or will largely compensate.

USE OF JARS

After some depth has been reached, or where boulders
threaten to ' 'stick" the drill bit, there may be occasion to
put on the jars not only to afford the impact necessary to
loosen the bit by the jerk they can exert, but also for their
added weight. Generally, however, they are quite unnec-
essary.



34 DRILLING FOR PLACER GOLD

PUMPING

When the operator has broken up and loosened the mate-
rial nearly to the bottom of the pipe he will throw the crank
wheel out of gear and the cable reel into gear, thereby hoist-
ing the tools clear of the pipe, and will swing the stem out of
the way usually throwing it over and behind the cross-arm.
One pail of water should be dashed over the stem as it rises ;
more water should be added before pumping, as previously
described. The Vacuum Sand Pump is then dropped into
the hole, and rapidly raised and lowered two or three times
to suck in the material. This pump contains a plunger
which travels through its whole length. The rapid dropping
of the pump forces this down and when the sand reel is
thrown into gear, this ' 'sucker" is drawn up so rapidly as to
produce a vacuum in the lower part of the pump, thus
opening the valve and drawing in the loosened contents of
the pipe. The secret of successful pumping lies in impart-
ing a properly rapid motion to this plunger and the power
and control of the Keystone Drill enable the operator to re-
cover the gravel, slimes, sand and mineral enrichment with
a remarkable thoroughness. Two pumpings are usual in
ordinary work where progress is made a foot at a time. Of-
ten time can be saved by pumping immediately after driv-
ing, drilling only when there remains more than 2 or 3 inches
of core. The two pumpings, the one before and the one af-
ter drilling, are preferably caught in the same pan and con-
centrated in one operation. When extraordinary care is not
required the material may be poured directly into the pan
which will have been placed across the frame of the sluice -
box, the slimes being allowed to accumulate in the box for
the final * 'clean-up" on completion of the hole the panner



DRILLING FOR PLACER GOLD 35

making proper record of the values therein contained. This
sluice-box, a wooden frame with a half-round trough of gal-
vanized iron, is mounted on wooden supports directly in
front of the drill and extending forward away from the pipe.
The attendant will carry the valve end of the pump out from
the pipe as the operator easily slackens the cable (not enough
but that the line still carries most of the weight of the
pump) until he can lay it over the box; then he will raise
the valve end and dump its contents into the pan. The
pump should then be washed clean, both inside and out,
with clear water and allowed to rest on top of the sluice-box
(so that sand-line and drilling cable do not touch) ready for
the next pumping.

CHECKING VOLUME OF MATERIAL PUMPED

If variable cores and unusual conditions suggest a greater
accuracy in the observation of the relation of the recovered
material to theoretical displacements, the entire pumping
may be at once emptied into the sluice-box. At its lower end
will be placed a large tub of water containing a pail into
which the material falls. The contents of this pail will be
measured before panning the tub will gradually collect the
slimes for the final accounting. The pail had better be cali-
brated and a chart prepared showing the cubic feet of mate-
rial for each inch which the surface lies below the top of the
pail. There is here given (Plate "E") an actual record of
such data as presented in the report of a well-known Engi-
neer.

DRIVING

After the pumping, the drill-stem will be swung back into
the hole and carefully lowered to rest on the surface of the



36 DRILLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 37

material within the pipe. A measurement should then be
taken to ascertain the amount of material above the drive-
shoe and record made thereof as "core after pumping."
The drive-blocks are then bolted on and the pipe driven the
proper distance, usually a foot, more in loose and easy
ground where no values are anticipated; less in very hard
and refractory gravel or resistant sand. It has already been
noted that there are occasions when lack of progress indi-
cates that one may reluctantly drill ahead to facilitate driv-
ing, but the Keystone Drill has ample power to cope with
exceptionally hard formations and the logs of Keystone
drill-holes are singularly free from record of this expedient.

FINISHING HOLE

Most holes are continued to the hard rock, shale, de-
composed granite, tufaceous lava, or barren stratum that
marks the limit of recoverable values. The Engineer will
usually prefer to be present at the conclusion of a hole, not
only on account of the greater concentration of material
usually encountered on bedrock, but to observe what he may
of the character of this formation. The pipe should be driv-
en to a depth that makes certain of bedrock and of the total
absence of values but not to a depth into the bedrock that
will make pulling a slow and tedious process. The full pur-
pose of the test hole having been supposedly now accom-
plished, the operator may, at will, drill a few feet into the
bedrock. This will prove whether his supposed bedrock is
or is not a large boulder.

PULLING PIPE

The long stroke of the Keystone Drill, together with its
responsive control, facilitates the withdrawal of the heavy



38 DRILLING FOR PLACER GOLD

drive pipe for use over and over again. The stem is de-
tached from the rope-socket and the "puller" screwed on
tightly. The puller knocking-head is then attached to the
top length of pipe and the machine started with the slack
so controlled as to strike a forceful upward blow. If the
pipe yields but slowly, the pulling ring and lifting jacks may
be employed. The water-level in the hole is usually meas-
ured during this operation, although, if the hole "stands up",
more nearly accurate information may be obtained by delay-
ing this reading for a day or so. When the last joint is
removed, the drill-stem is again fastened to the rope-socket,
loaded into the bed of the machine, the jacks removed,
and the outfit moved to the next hole.

PANNING

Under ordinary conditions the panner will concentrate
the recovery of each pumping in his pan. After removing
all but the minerals and black sand, he will estimate the
weight of gold in milligrams and also count and record the
colors. It is customary to record these as of the "First",
"Second" or "Third" grade. A "Third" grade color is one
that is large enough to be individually counted, yet below
two milligrams in weight. A color between 2 and 7 milli-
grams is of the "Second" grade above 7 of the "First"
grade. This counting of colors and estimate of weight
serves several purposes. It shows the occurrence of values
according to the depths ; it gives data for the Engineer if the
recovery of a pumping is to be later discarded or discounted ;
it gives some idea of the worth of the ground if by accident
the recovered values are lost or contaminated. The gold
from the various pannings as the hole progresses will be ac-



DRILLING FOR PLACER GOLD 39

cumulated in the same globule of mercury. This, preserved
in a glass tube, will be kept on the person of the panner. On
finishing the hole the tailings will all be re-run through the
rocker, together with the slimes from the sluice-box and tub,
and any values added to the mercury. This will then be
handed to the Engineer, together with the log of the hole
which it is also the panner's duty to keep. When the drill-
ing is being prosecuted by a night-shift it has proved unwise
to attempt panning by artificial light. Under such circum-
stances the pans are preserved for concentration on the fol-
lowing day, being marked by a wooden "paddle" on which
the proper identification of the pumping may be pencilled.
The panner is held responsible for the correct recording of
the progress of the work, of the cores and for the recovery of
every particle of metal.

TIN PROSPECTING

The procedure in evaluating tin placers is practically the
same as for gold except that the panner will screen his ma-
terials and grind the larger particles of tin to determine a
sample and gain an assay that will declare as to the propor-
tion of dross in the heavy tin-stones. Placer gold particles
are ordinarily unadulterated with quartz not so with tin

"nuggets".

PLATINUM

Inasmuch as platinum is not picked up by the mercury, it is
necessary to save for assay the heavier concentration of the
pannings. In rare cases, the platinum will represent no small
proportion of the values in all placer fields it is a wise precau-
tion to make a careful test of its presence in commercial quan-
tities. For the ordinary gold-saving, tables of the modern
dredge make a remarkable recovery of these heavy particles.



40 DRILLING FOR PLACER GOLD

FIRE ASSAYS IMPROPER

Every Engineer has heard of instances where through
ignorance the concentrate from auriferous gravels has been
sent to the assay office for a fire test. This grave error is
even today not uncommon. It should be remembered that
the heavy quartz pebbles carry gold that no washing device
can recover and that while field panning and hand concen-
tration methods may be crude, that they are of comparable
efficiency to the gold-saving devices of the dredge and that
more nearly accurate recovery from the sample will be dan-
gerous and misleading. The ' 'black sand" concentrate from
the bottom of the pan, after the mercury has picked up all
visible yellow particles of gold, will often yield a high fire
assay but the recovery of these values by washing or amal-
gamation is even more nearly impossible on a large scale than
it was in the prospector's pan!

PRECAUTIONS TO BE OBSERVED

On leaving the work at the end of a shift, it is an excellent
idea to throw into the hole a few handfuls of tailings that are
known to be barren. This is pumped out and inspected on
beginning the next day's work an effectual safeguard
against tampering. In fact, it is impossible to salt a Key-
stone Drill hole if even moderate watchfulness is employed.
It is rumored that on one occasion particles of virgin gold
were inserted into the fibres of the drill-rope, these gradual-
ly falling into the hole as the work progressed. The sight
of a few flakes of bright gold on the top of the driving-head
revealed the trick. It is also said that once an interested
property owner loaded a cigarette with precious dust and
flicked the ashes into the pan as concentration was being



DRILLING FOR PLACER GOLD 41

carried on. Salting is only possible by some such fantastic
and wholly unlikely ingenuity. However, the careful Engi-
neer will from time to time check the purity of the quick-
silver which he uses.

FROZEN GROUND

A new technic of drilling in the frozen gravels of the Arctic
has been developed. This work requires experience if it be
done with accuracy; we can only touch on the method em-
ployed. When the pipe reaches frozen strata, drilling and
pumping and panning proceed below it a foot at a time.
There will be some caving, and an irregular hole is pretty
sure to result as thawing proceeds. After bedrock is reached,
the tools are withdrawn and a measured quantity of water
kept at a temperature just above freezing is poured into the
hole. A careful record is kept of the volume necessary to
raise a float one foot vertically and thus is secured an equiv-
alent measurement of the cubic feet of gravel actually re-
moved in each foot of progress. With the new science of
"cold-water thawing" and the renewed interest in Arctic
gravels, this ingenious method of insuring reasonable accura-
cy in prospecting becomes particularly noteworthy and
here again is the power of the Keystone Drill of signal value !

UNUSUAL CONDITIONS

The vast differences encountered in probing the placers
of the world cannot all be dwelt upon in this short treatise.
Indeed, there will be unprecedented conditions now and then
arising that will tax the resourcefulness of Engineer and op-
erator alike. But the ruggedness and yet splendid flexi-
bility of the Keystone Drill adapt it to the hardest tasks.
It can be cribbed up high above marshy ground when long



42 DRILLING FO R PLACER GOLD




DRILLING FOR PLACER GOLD 43

pipe lengths are to be handled. It can be operated from a
scow afloat in lake or river. It is a sturdy machine for
hardy men in rough country!

Here might be introduced a paragraph on the Keystone as
a Shaft-Sinker in frozen strata. The advantage and process
are that : A six-inch hole is first drilled through the frozen
strata. Two or three returns of one-inch pipe connected to
the boiler serves overnight to thaw the material out to
shaft size. The drill-stem having been removed, the cable
and cable reel are, without other change, used to elevate the
mining bucket for the thawed material or the accumulated
water. The machine and its accessories in fact make it a
complete shaft-sinking outfit.



HARRON, RICKARO * MeCONE
SOLE AGENTS



CHAPTER III

LAYING OUT THE GROUND AND
ESTIMATING THE VALUES

SURVEY

The careful examination of a placer deposit requires a thor-
ough survey and an adequate map this being made with
sufficient accuracy and to so large a size that distances may
be scaled with precision. It is not always possible to secure
such a survey in advance the Engineer will often prosecute
such work while supervising the beginning of drill work.

WHAT MAP SHOULD SHOW

On the map should appear property lines, roads, bedrock
outcroppings, and physical limitations of dredging areas; and
it should represent a complete picture of the property not only
for purposes of prospecting, but for later use in buying par-
cels of land and for dredge operations: Perhaps such thor-
ough work will not be completed until there is some assur-
ance as to the desirability of actual exploitation, but the
initial survey may quite as well be conducted so as to be
made full use of if the property ''proves up".

PLOTTING DRILL HOLES

Usually the first drillings will render a verdict as to the
ultimate value and dredgability of the property. Accord-
ingly, it is often desirable that they be well scattered so that
they may roughly reveal the worth of the entire acreage.
Yet, if the results are favorable, this first work should have
been so done that it fits into the complete campaign of
prospecting.



DRILLING FOR PLACER GOLD 45

EXPLORATION WITH DRILL

In a channel deposit the Engineer will often stake out
lines at right angles to the stream flow and mark proposed
holes just as if he were assured of favorable results. Then
he will start drilling by driving alternate holes on alternate
lines with the purpose of later completing the work when
the value of the area has been reasonably established. In a
"blanket" deposit he may chart his entire scheme of drilling
then actually drill here and there over the entire acreage
until a complete exploration has been justified.

LAYING OUT HOLES IN STREAM DEPOSIT

In all ordinary deposits a Keystone Drill hole to every two
to four acres will be adequate to yield complete data as to
values. The plotting of proposed drill-holes will be made
with this in mind. Several "channel" or stream deposits
have been appraised by drilling holes at a distance of 150 feet
on lines that are 1000 to 1500 feet apart. The location of
holes on Plate "A" is typical.

"BLANKET" DEPOSITS

As is hereafter described, the marking of a wide acreage
of auriferous gravels into equilateral triangles, placing drill-
holes at their apices, is an excellent method of conducting an
exploration. The final calculations are then quite simple
and the chance of confusion and error is eliminated. Some
Engineers prefer to plot the field in rectangles, drilling at the
corners of each parcel. Still others divide the field into
squares and drill at the center of each square. This brief
treatise does not attempt to argue the merits of various
methods but to fully present one method for the uniniti-



46



DRILLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 47

ate and record the several angles of consideration as memo-
randa for the more experienced.

TREATMENT OF AMALGAM

The Engineer will receive from the panner a small phial
in which he has preserved the mercury containing the gold
from the sample. This he will treat with dilute nitric acid
(Sp. Gr. 1.42 plus an equal volume of distilled water) in a
test tube over the flame of an alcohol lamp wash well with
boiling water to which a few drops of alcohol have been
added dry and anneal in a small annealing cup or porcelain
crucible and weigh the clean dust on scales that are accu-
rately sensitive to a milligram. Pocket scales are made that
are sufficiently precise for this work. These operations should
be carried out in a room free from dust or air currents and
with clean reagents and containers. Then the Engineer,
with the weight of the gold and the log of the hole before
him, proceeds to the calculation of values in "cents per cubic
yard" the accepted basis for the evaluation of placer prop-
erties.

DETERMINING FINENESS OF GOLD

To properly translate his gold values he must appraise the
fineness of the metal peculiar to the property in question.
Many Engineers insist on sending a sample of the gold col-
lected to the nearest available authority on quantitative
analysis to determine with accuracy the proportion of gold
and silver. Sometimes, if platinum be expected as occur-
ring in the sands, as large as possible a sample of the panner's
concentrate is also sent and a determination of that metal
likewise requested.



48 DRILLING FOR PLACER GOLD



VALUE OF MILLIGRAM OF GOLD

A customary approximation, when accurate data are lack-
ing, is to call a milligram of gold worth .06 cents. This is
based on gold that assays $18 . 66 worth of pure metal to the
troy ounce of 480 grains one grain being equal to 64 . 8 mil-
ligrams.

CALCULATION OF CUBIC CONTENTS
OF DRILL-HOLE

A 1 foot hole yields .3068 cubic feet of material. If that
material produces 1 milligram of gold then a cubic yard will
produce 2 7 /. 3068 times as much or 8.8 milligrams.
But, on a basis of gold that is worth $18 . 66 per ounce; one
milligram is worth . 06 cents. Therefore a hole one foot in
depth that yields one milligram of gold proves a value of 8 . 8
times . 06 or 5 . 280 cents. Then, since this figure repre-
sents the yield of a hole of the unit depth of one foot and the
unit recovery of one milligram we have only to divide it by
the depth in feet and then multiply it by the number of mil-
ligrams recovered to learn the indicated values in cents per
cubic yard for any hole ! A table is included in this booklet
which reduces this arithmetical calculation to one operation.
(Plate "G"). It is based on the working out of the following
formula :

3068 X x P t p,, x Mgms. = Value in Cents per Cubic Yard.

. 3068 Equals area of drive shoe in square feet.

27 Equals conversion factor to cubic yards.

. 06 Equals value of gold in cents per milligram.

"D" Equals recorded total depth of hole in feet.

Mgms. Equals number of recovered milligrams.

In this appended table there have been substituted vari-
ous depths for the factor "D" there remains only to multi-



DRILLING FOR PLACER GOLD 49

ply the partial result opposite to the actual depth to bedrock
by the number of milligrams to find the indicated value in
cents per cubic yard.

COMPENSATION FOR EXCESSIVE CORES

Occasionally a hole will be reported that varies in a
marked manner from normal. For instance, suppose that
between the 20 and 25 foot marks there was trouble with a
defective pipe joint or a plugged core that kept out the proper
amount of material or an inrush of far too much sand
and gravel. The panner's log would show an estimate of 18
milligrams of gold in this five feet of progress and extracted
from either too little material or too much. Suppose that
the amount of material actually recovered and the theoreti-
cal recovery do so fail to coincide, what then? Some Engi-
neers prefer to throw out this portion of the hole ; it is surely
not necessary to discard the whole drilling by reason of this
mishap, nor yet should such unreliable data be incorporated
as part of the whole. In this hypothetical case the Engineer
would subtract five feet from the recorded depth and 18 mil-
ligrams from the weight of the gold as finally wieghed ; then
calculate his values. Other Engineers will credit values to
this five feet of hole according to the average of a like dis-
tance above and a like distance below the error. This seems
a likely way to approximate the truth.

OTHER CONSTANTS IN COMMON USE

But the constant of . 3068 (based on the calculated volume
of a cylinder 1 foot high with a base l l /2 inches in diameter)
is only one of several that have been widely used in the past
and are more or less favored today.



50 DRILLING FOR PLACER GOLD

CONSTANT OF .3333

It was once a favorite practice to estimate values on the
above basis and then to discount the completed returns on
the appraisal of the property by 10 or 15 per cent as a meas-
ure of safety and conservatism. However praiseworthy
this desire to err only on the side of safety, this procedure is
hardly professional or sensible. At least one serious error
has occurred where the values were so discounted twice
through a misunderstanding. But this desire to lean to the
safe side led to the adoption of an arbitrarily fixed constant
of .3333. This was widely used by those who insisted on
ultra-conservatism in the estimating of dredging values and
also by those who maintained that the beveled edge of the
Keystone drive -shoe as well as the entire method of opera-
tion allowed more material to enter the drill-pipe than
strict theory would indicate. The use of the constant . 3333
gave final values that were 8.7% less than when the .3068
factor was employed.

KEYSTONE CONSTANT OF .27

But from the very earliest day of the development of the
technic of prospecting, there have been many Engineers who
have favored the constant of . 2 7 (one cubic yard of material
to each 100 feet of pipe). This has been widely called the
"Radford Factor" or the "Keystone Constant." Its use
was first scouted as too likely to exaggerate values, but in
the light of recent comparisons of estimated prospecting to-
tals and the actual recovery of subsequent dredge returns,
this "Keystone Constant" climbs back into secure favor.
One large Company that has successfully operated many
dredging properties in different parts of the world for a long



DRILLING FOR PLACER GOLD 51

time preferred the conservative constant of . 3333 but it is
noteworthy that their estimates today are usually worked up
on the basis of the " Keystone Constant."

REASONS FOR THE KEYSTONE CONSTANT

The churn drill, functioning by impact", continually acts
to drive the gravel downward before the pipe and to settle
the heavier particles of gold and precious metal. If any
metal ever does escape the action of the pump, it is more
likely to be these same heavier particles. At the conclusion
of the hole the last drilling may have driven a few particles of
the metal down out of reach into the bedrock. The panner
may always, despite the most scrupulous care, lose a tiny
proportion of the values from the splash of the pumping or
in the rocker. There is more likelihood of missing some of
the values than of getting more than the due amount.
There are many sound reasons to justify the practice of
crediting the recovered gold to a volume of material some-
what less than the theoretical amount and the "Keystone
Constant" does just that.

NO ONE CONSTANT INVARIABLY PROPER

Few Engineers will use the same constant under all con-
ditions. For there are many variables to consider in trans-
lating the work of a drill to a well considered prophecy of the
values that the dredge will recover. The Engineer, in
choosing his constant will weigh many things. The per-
sonality of his crew cannot be ignored. The time of the year
in which the work is done will have an effect a panner can-
not work in freezing weather with the same accuracy as in
the pleasant days of summer. Rich and streaky channels of



52



DR I LLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 53

heavy gold concentration will usually drill higher than the
expected recovery a small gold content evenly distributed
in loose ground will often show to the drill as less than what
the dredge will later actually save. These matters will be
discussed more at length in the final chapter of this article
"Chapter IV Reliability of Keystone Samplings".
Most Engineers today will use the "Keystone Constant" as
the proper basis for their estimates.

COMBINING VALUE OF VARIOUS HOLES

When the Engineer has correctly evaluated the various
holes he faces the problem of combining them to gain his
tract values. It is customary to plot the holes on a large
map, noting dredging limits as determined by surface con-
tour, by exposed rimrock or reefs and also marking proper-
ty lines. If the values fade off into barren areas there should
be marked the probable boundaries of dredging values
roughly estimated at the probable cost of the dredging
operations. This may vary from 5 cents where a large
dredge is to work under the most favorable conditions to
1 5 cents or even more where inaccessibility, expensive power
or frozen ground offers difficulties. If the ground shelves to
shallower depths the limiting depths should also be plotted.
These vary for different dredges, but the average dredge can
hardly dig its flotation in ground that is not at least 12 feet
in depth. The yardage should be estimated from this com-
pleted plat with all possible accuracy. It is perhaps true
that a little carelessness or a wrong conclusion at this point
will affect the figure of total recoverable gold more than any
other error that is likely to be made. It may be noted in
passing that most Engineers add to their yardage calcula-



54 DRILLING FOR PLACER GOLD

tions the amount of ground that the dredge buckets will
handle in digging bedrock to the depth of one foot. This is
a necessary procedure in actual dredging and one that dilutes
the auriferous gravels with barren material.

PRINCIPLE OF EVALUATION

The only principle involved in calculating the value of a
tract of ground lies in the necessity of giving proper "weight"
to each drill-hole in that area that is, in letting a drill-hole
affect the final result in proportion to the area which it rep-
resents, or "governs." Merely to add the values of the
holes and divide by the number of them is an elementary
error.

CALCULATION WHEN HOLES ARE SPACED
EQUIDISTANTLY

If the area of auriferous gravels is a "blanket" deposit and
it has proved feasible to lay out the holes so that they are
equi -distant, this calculation is a simple one indeed. The
ground is then divided into equilateral triangles, and the
depth of each area, and its values in cents per cubic yard is
the average of the product of the depths and values of each
hole. Thus, the deeper the hole, the greater its effect on the
values of the area. The value of the tract is the average of
the products of the volume of the triangles and their values.
If the holes are not evenly spaced, to connect them by lines,
to figure the area of the enclosed triangle and to allot to it
the average of the products of the depths and values of the
three holes at its apices is not far wrong. . To be sure, there
is a slender factor of error that increases as the "triangle"
departs from the equilateral, but this is a compensating
variation that may often be ignored.



DRILLING FOR PLACER GOLI> 55

OTHER METHODS

There are Engineers who favor other and more compli-
cated calculations but the principle to be followed is a sim-
ple matter of common sense that lends itself to translation
in ordinary arithmetical terms. Discussion of the infinite
number of special problems that the prospecting Engineer
will meet can only bring one back to the starting point. It
has been shown by actual test that rarely will two Engineers
go about combining the results of two or more drill-holes in
exactly the same way. But there is little chance to go far
wrong. If there be a large area and many holes, the result
will surely be within the limits of error of the entire technic
of field work ! Set several men to counting a pile of nails
some will count one at a time ; some two at a time and some
five at a time but the complete tally will be the same no
matter what system best fitted the idiosyncrasy of the coun-
ter! The best argument against meticulous precision or
vast elaboration in the calculation is the admitted fact that
the same Engineer cannot get the same results from the
evaluation of the same scattered holes at two different
times. But the percentage of disagreement will be well
within safe limits. To be sure, there are occasional per-
plexing problems where the odd areas at the side are of un-
usual shape, or where it becomes necessary to separate the
value of some particular tract or acreage from the calcula-
tion of the whole area. But these, too, yield to arithmetic
and to the elementary principle of allowing each .drill-hole
to influence only that territory to which it is the nearest.
"HIGH HOLES"

Two or three of the holes are most likely to be very much
higher than the others. Sometimes, they are so large in com-



56 DRILLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 57

parison with surrounding holes that there is a very natural
suspicion of a grave error. There is no standard method of
treating these "high holes" in the final calculation differ-
ent Engineers favor different methods. In fact, nowhere
does the "personal" factor enter more strongly than in mak-
ing the decision as to how such high holes shall be counted.
Some hold it advisable to put down a check hole about six
feet from the high hole. The check hole rarely shows values
as great sometimes it is surprisingly low. Usually, the
average of the high hole and check hole is taken and figured
into the final result as though there were but one hole at
that point. It may be here noted that the gold content of
more than one property has been padded by figuring in the
check holes on an equal basis with the other drillings, the
fact being forgotten or ignored that these holes were put
down at favored locations and were not equally representa-
tive samplings. Usually, the Engineer is content to check
one or two of the high holes and to regard the others in the
light of what the first check holes reveal. If the property
as a whole is of even enrichment, there is little likelihood
that a second hole will confirm exceptionally high results of
a first. On the other hand, if it is known to be "spotted",
an occasional high hole can be accepted at full value without
question. Indeed, the plotting of the several high holes
will sometimes indicate a rich streak or channel. Extra
holes are often put down to determine the course and extent
of such an area of attractive concentration not as check
holes, but as supplementary drillings. Once that such an
enrichment is established, there is of course no argument
against accepting the higher values of the holes within such
territory. If the high yield of a hole can be traced to a



58 DRILLING FOR PLACER GOLD

single large piece of gold, or a nugget, it is customary to leave
out the weight of this persumably accidental bit in calcu-
lating the value. Some Engineers, in what is perhaps an
over-anxiety for conservatism, do not include the high holes
in their final calculations. Still others cancel them against
the low holes in the apparent conviction that the very
high and the very low are due to errors which may be bal-
anced. Another method is to take half the result of a high
hole which is more a concession to timidity than to com-
mon sense. Most dredge operators will report that a high
hole is never proved up by the work of the dredge. Yet
from actual results it seems to be an established and a safe
and proper practice that the occasional high hole may be
included in the calculations if it was correctly drilled and
if there is no mechanical error to be detected. For if the
drill caught a stray bit of concentration behind a boulder or
tapped a random streak of enrichment, there are quite cer-
tain to be many scattered areas of similar values that the
dredge will recover. It seems fallacious and hypercautious
to count out the one or two holes of most attractive result.
But it must be remembered that only very rarely does such
a high hole actually reveal a definite area of surrounding
yardage of a corresponding richness only adequate check-
ing could prove that! But it does have a proper part in
the summation of the whole!

CALCULATION OF STREAM CHANNEL VALUES

If the auriferous gravels follow a comparatively narrow
and well-defined channel, it will have been prospected by
lines of holes that cross it at intervals of a thousand feet,
more or less, the holes spaced rather close together, depend-



DRILLING FOR PLACER GOLD 59

ing on the width of the channel. The calculation of the
values of the line may be made as is outlined and exemplified
on Plates "A", "B," and "C." The principle is exactly the
same as has been above outlined. Each drill-hole governs
the length of "line" that is nearer to it than to any other
drill hole. The figuring is facilitated by making a diagram
of this channel cross-cut being careful to lay out the dredg-
able limits at the side with due regard to the surface contour,
bedrock elevation, barren gravels and practical digging
depths. Ordinarily, the line will end at an actual drill-hole,
but sometimes it will seem reasonable to extend it somewhat
beyond a hole with acceptable values and depth part way to
another hole that is either shallow or barren, or toward a
further and approximated dredging limit. It is then nec-
essary to credit to this "proportionate point" or "fictitious
hole" a calculated value and depth these assumptions to
be made with due regard to the comparative distance of the
two drill-holes that govern the estimate. This is shown on
Plate "A" there are such "proportionate points" at the
right limit of Line 9 and at the left limit of Line 10. No
matter if the holes be spaced irregularly, the area which
each governs may be visualized and correctly calculated.
To simplify calculations, the method exemplified in Plates
"A" and "B" is often resorted to the value of the area be-
tween two holes is estimated by multiplying the distance by
the average depth and the value. A study of the Plates
will reveal the whole process as reproduced from an actual
report. To obtain the value of the "block", or the dredga-
ble area between the two lines, the procedure as illustrated
on Plate "D" may be followed. The calculation is some-
times called the determination of block values by the "Cen-



60 DRILLING FOR PLACER GOLD

ter of mass" formula. The lines are projected (by using the
cosine of the angle which they make with an ' 'altitude" line
connecting their centers) and the average area of the pro-
jected bases, multiplied by this altitude, gives the volume of
the "block." It should be noted that the lines affect the
total value of the enclosed block not by their comparative
lengths but by the area of the channel that they cut.
In the same way, the blocks may be added to find the total
yardage and total gold content in a property but the
average value per cubic yard must be figured by allowing
each block to affect the result in proportion to its yardage.
Thus, the block yardages times the block value, added, di-
vided by the sum of the yardages will give the value of the
tract. It is often desirable to estimate as nearly as may be
the value of a piece of land within certain property lines
often so bounded as to have only one or two holes actually
within its confines. The calculation may be made by the
use of "proportionate points" or fictitious holes which are
credited with a depth and a value that are derived from com-
bining the value and depth of the two nearest holes in a pro-
portion that is in inverse value to their distance away.
Such estimates can be called little more than "intelligent

guesses."

SUMMARY OF CALCULATION METHODS

In the discussion above, the plotting of the cross-cut of a
channel has been pre-supposed. Referring to this drawing,
the Area between two holes, which is ordinarily a trape-
zoid, is the average of their depth multiplied by the distance
between them ; the Value of this Area is the average value
of the two holes multiplied by the Area ; the Value of the
Line is the sum of all these products divided by the Area ;



DRILLING FOR PLACER GOLD 61

the value of the Block is the sum of all these products in
one Line, plus the sum of all these products in the second
Line, divided by the added Areas of the two cross-sections,
and multiplied by distance between the lines.

WHAT REPORT SHOULD COVER

The experienced Engineer will include in his final report
of the property much beyond the mere calculation of yardage
and values. For it is quite possible that that very report
will be the dredge designer's sole source of accurate data re-
garding the physical conditions with which the dredge must
cope. Modern firms prefer to design a dredge to fit the
property. Even a used dredge, if torn down and trans-
fered to a new property must be largely altered to meet the
somewhat different conditions of soil and depth. Accord-
ingly, there are here suggested the various bits of infor-
mation upon which a thorough report will touch :

Character of bedrock.

Water-level with reference to surface and to bedrock.

Are boulders present? Their maximum size.

Character of gravel loose, cemented, clay, etc.

Kind of gold large or fine ; flaky or rusty.

Are special gold-saving devices indicated for nuggets or
for flour or oxidized gold?

What are climatic conditions on property? Must dredge
be specially equipped to lengthen its working season?

What are transportation conditions with special refer-
ence to heavy dredge machinery?

What power is available for dredge construction and
operation? Its probable cost?



62 DRILLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD . 63

What is recommended size of dredge for efficient operation
and for proper exploitation of available yardage?

What about water supply?

What is maximum grade of ground in which dredge will
be called upon to work?

Where may dredge be best built with relation to greatest
conveniences for construction and good values as well
as in accord with the best economic plan for future
operations?



64 DRILLING FOR- PLACER GOLD




CHAPTER IV

RELIABILITY OF KEYSTONE
SAMPLINGS

Actual Instances of Comparison Between
Drill Estimates and Dredging Returns

KEYSTONE ESTIMATES NOW CHECKED

If gold particles were uniformly distributed, uniform
samplings would exactly determine the value of the whole.
But the precious flakes are laid down according to no mathe-
matical law; rather by the uncertainties of shifting currents,
of spring freshets, of endless reconcentrations. Even a defi-
nite ' 'pay-streak" begins unexpectedly and ends abruptly.
Seldom will a dredge recover a comparative amount of gold
in two successive days of operation. Yet the records of a
generation of placer gravel exploration have proved that a
reliable appraisal is quite possible with the Keystone Drill.
Yet Engineers rarely expect a second drill-hole, sunk a few
eet from a first, to yield values that are in close accord;
nor are they surprised when a shaft, put down around a
drill-hole, presents a considerable discrepancy in values.
No one expects a flake of ore, chipped from one part of a
vein, to assay the same as another flake from near-by.
Yet the average of several such flakes will approximately
reveal the proportion of mineral in the ore-body. The the-
ory of Keystoning is the theory of averages let the sam-
ples be fairly collected, correctly measured and properly
assayed and they will collectively indicate the values of the
whole. Once this was purely theory today it is fact.

65



66 DRILLING FOR PLACER GOLD

For in the last few years the results of vast dredging
operations have been totaled and analyzed, and it is
now possible to check them with the predictions of
those who drilled the same areas in earlier years.

AGREEMENT ON OREGON PROPERTY

A placer deposit in Oregon which was the result of stream
action was systematically drilled by lines of holes at right
angles to the flow. The work was carefully done by com-
petent Engineers and the calculations carried out by the
methods illustrated in Plates "A" to "D." This property,
consisting of 121 acres, has today been completely mined by
a modern dredge. Its average depth was 18 feet and there
was an overburden of almost barren tailings covering a
"streaky" enrichment. The original estimates gave the
average value per cubic yard as 16.8 cents and the value
recovered by the dredge was 15.63 cents or 93% of the
estimate. The constant used in computing the drill re-
sults was . 3333 ; had a constant of . 3068 been used, the esti-
mated and actual values would have agreed quite closely.
There were here put down one hole to every 2 . 4 acres.

Yet hardly any two of the eight "blocks", into which the
area was divided by the drill lines yielded the identical
values which the drill forecast in one of them the recovered
value per cubic yard exceeded the estimate by 49 . 4% and
in another it was less by 68 . 2%.

CHECK ON A CALIFORNIA PROPERTY

We reprint from the Engineering and Mining Journal an
account of the balancing of prospecting estimates and dredg-
ing results on a California property section of 118.5 acres



DRILLING FOR PLACER GOLD 67

where the results of 38 drill-holes were used in making the
forecast 14 of the holes being outside but adjacent to the
area dredged.

"The estimated value per cubic yard in this tract was
29.88 cents and the dredge returns were 31.55 cents, a
gain of 5 . 6%. We believe the constant used in figuring the
drill returns on this property to have been .3068. Some
years ago on another and undredged portion of this property
consisting of 493 acres an estimate was made to determine
the gold content. The results from 53 drill holes, which
were within the limits of the tract, were used by taking 70
per cent of their recorded value. Consideration was then
given and use made of the values obtained from dredging
operations which had been conducted adjacent to and
around about two thirds of the tract. Since then 402 acres
of this tract have been dredged and the returns per cubic
yard averaged 12.73 cents. The data used in making the
original estimate were applied to the portion now dredged
and the proportionate values found to be 12.70 cents per
cubic yard."

ANOTHER CHECK FROM LARGE ACREAGE

From the same article we quote another example that
shows a recovery closely corresponding to the estimate,
giving the results produced by operations on three separate
tracts in a large California property, the third tract having
been mined by three dredges:



Average


No. of


Acreage
to Each


Value per Cubic Yard
Dredge Per-


Tract


Depth


Acres


Holes


Hole


Drill


Recovery centage


A




22


.5'


173.


5


x 57


3.2


6.8


7


.82


115%


B




44


.5'


84.





20


4.2


5.9


6


.7


113%


CDr.


#1


51


.8'


183





120


1.5


11.1


9


.64


87%


CDr.


#2


60


.6'


106





41


2.6


11.2


9


.44


84%


CDr.


#3


56


.4'


135





58


2.3


11.6


11


.30


97%



68 DRILLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 69

x 37 shafts and 20 Drill-holes

On Tracts A and B Constant Used in Calculating Drill Results . 27

On Tract C Constant Used in Calculating Drill Results . 30

CHECK FROM SMALL DREDGE OPERATIONS

"The average results of all the above, proportioned to the
acreage, is a drill value of 9.48 cents per yard, and the
dredge recovery 9.12 cents, or 96 . 2%".

And we quote yet another instance:

"Dredging operations on one property in California have
produced returns which, taken as a whole, correspond quite
closely with the original estimates, and the following de-
tails have been presented covering the work done in the past
three years:



Year


Average
Depth


Acres


No. of
Holes


Acreage
to Each
Hole


Value per Cubic Yard
Dredge Per-
Drill Recovery centage


1918
1919
1920


32
34
29


I 7
4'
8'


19
20
20


94
90
43


11

10

7


1.8
2.1
2.9


10
9
10


39
69
.69


10.64
9.22
14.34


102.4'
95. 2<
134.0'


3
1



EXAMPLE FROM OPERATIONS OF NATOMAS CONS.
OF CALIFORNIA

"The average results proportioned to the acreage show an
estimated value of 10.25 cents and a dredge recovery of
11 .39 cents, or an increase of 11 . 1%".

Perhaps the dredging problems of the Natomas Company
of California have been the most difficult encountered on
large scale operations. Here, on the American River, are
high benches of gravel that is so compact and cemented as
almost to defy the dredge buckets and, down in the
bottom lands, wide areas of softer and shallower ground.
A check, made five years ago on the operation of three of
their many dredges gives a reasonably close agreement.



70 DRILLING FOR PLACER GOLD

Percentage of

Area in Years of Estimate

Dredge Acres Operation Recovered

No. 5 180 10 86

No. 8 106 4 87

No. 9 135 6 101

These results are based on an original calculation using
the constant .30. During the last five years these dredges,
as a whole, have produced about 101 per cent of the cal-
culated recovery !

MONTANA PROPERTY

A portion of a Montana property consisting of 300 acres
was prospected with 77 drill holes spaced at irregular dis-
tances. The average value per cubic yard indicated by the
drilling was 15.83 cents, and the dredge recovery 13.55
cents or 85 . 6%. The average depth of the ground was 40
feet and the larger portion of the values was contained in
the three feet of gravel next to the bedrock. Such a deposit
offers obvious difficulties to accurate calibration.

TABULATION OF AVAILABLE COMPARISONS

The article from the Engineering and Mining Journal
partly reproduced above, written by Mr. Charles W. Gard-
ner, Manager of the Mines Operating Department of the
Hammon Engineering Company, probably the first Engi-
neer to use a Keystone Drill for placer prospecting, con-
cludes with a summary that is of striking interest :

"From all of the properties above mentioned we are able
to segregate 3,743 acres to which we can apply data given in
fairly accurate reports. This combined area was pros-
pected by means of 1,749 drill-holes, or one to every 2.1
acres. The average value per cubic yard obtained by



DRILLING FOR PLACER GOLD 71

drilling was 15.4 cents and the average dredge recovery
13 . 55 cents, or 88%. A comparison of returns, segregated
as to values, is as follows :

Average Value per Cubic Yard Percen tage

Drill Values per Per Centage Drill Dredge

Cubic Yard Acres of Whole Value Recovery Gain Loss

Underll^ 27.9 0.7% 9.2M 8.60^ 6.6%

Underll^ 1638.1 43.8 7.68 9.34 21.6%

Between 11 and 12 c 424.0 11.3 11.28 10.12 10.3

Between 11 and 12 e 480.0 12.8 11.61 16.44 41.6

Between 12 and 20 c 582.5 15.6 16.92 13.10 22.6

Over 20 c 392.0 10.5 45.86 20.93 54.4

Over20c 198.5 5.3 33.15 35.97 8.5

Totals 3743.0 100.0%

AVERAGES 15.40 13.55 12.0

Here is spread before us the work of different Engineers
at different times in many fields. There has been no at-
tempt to trace out the avoidable error in either prospecting
or mining. Suffice it to say that there is included in this
tabulation the exploration of at least two properties where
the excavated material was a clean washed sand and gravel
with little clay and many boulders ; making the forecasting
of the values exceedingly difficult by any method and the
recovery of certain dredges that fall short of the highest
standard of modern efficiency.

ACCURATE PROSPECTING POSSIBLE

Mr. Gardner closes his article with; "We feel that a safe
conclusion to be drawn from all of the above is that when a
property has been sufficiently prospected by an experienced
Engineer, the results intelligently interpreted and the cal-
culations accurately made, the result obtained will indicate
within reasonable limits the gold content.



72 D R I LLING FOR PLACER GOLD




DRILLING FOR PLACER GOLD 73

"Full consideration should be given all these points and
then if the estimated gross value safely and sufficiently ex-
ceeds the cost of acquisition, equipment and operation,
there should be nothing to deter or discourage the invest-
ment of capital in such an enterprise."

HOW DIFFERENT CONDITIONS AFFECT
ACCURACY

Mr. James W. Neill, in an article in the Mining and Sci-
entific Press, says, "If the driller keeps his bit behind his
shoe, and sees that he gets a correct amount of core, there
should be little question of the correctness of a large gen-
eral average, and the Engineer can use such factors of
safety as his experience and the character of the ground in-
dicate. In very loose ground, I personally look for a recov-
ery of full drill values where the gold is coarse and is entirely
contained in the foot or two above bedrock. I think one
will also usually overrun the drill, provided the bedrock can
be dug. That is about the sum of our experience at Snelling. ' '

We quote an extract from an article by the compiler of
this booklet that recently appeared in the Engineering and
Mining Journal; "It may be observed that the accuracy of
results gained by drilling is surprising, considering the com-
paratively small size of the sample. For example, one hole
to two acres in 50-ft. ground would mean that 1 /328,000
part of the gravel was examined. Of course one hole by it-
self means nothing it is only a carefully charted series that
reliably represents actual conditions.

"All available data seems to point to the following facts
regarding the accuracy of drilling :

1. Drill results give high assays where the gold is fine.



74 DRILLING FOR PLACER GOLD

2. Estimates will tally with returns where gold is reasona-
.bly heavy; ground is compact with a little clay; and

prospecting and dredging are intelligently done.

3. The drill will exaggerate the value of very loose ground
where sand and water pressure crowd material into the
bottom of the pipe.

4. The drill will signally' fail to show recoverable gold in
areas of moderately loose ground where gold is dis-
tributed and in comparatively small amount."

SUMMARY

The whole problem is squarely up to the discretion of the
Engineer. He may compensate for the co-efficient of the
personal accuracy of his crew; he may use the proper con-
stant in his calculations ; he may use his own experience and
the now recorded findings of others and translate the
results of his Keystone Drill work to a forecast that bears
the stamp of conviction and accuracy !



CONCLUSION

The Keystone Driller Company sells more
than a mere machine it sells service! Orders
are carefully filled with selected materials and
shipments forwarded with all possible expedi-
tion for we are keenly alive to the difficulties
and hazards of field work. During the score of
years in which Keystone Drills have been the
reliance of prospectors the world over, we have
collected a considerable knowledge of the technic
of placer testing and of the proper equipment
therefor. That data we shall gladly share ; and we
offer our experience to any Engineer, be he out-
fitting for a proposed campaign of prospecting
or meeting a knotty problem in the field!



75



76



DRILLING FOR PLACER GOLD



PLATE "A"




LINE No. 9
Hole 29 49.5'
Hole 30
Hole 31
Hole 32
HoleX



30'
189'
192'
197'
116'
20'

Width at top 744'
Width at bottom 694'



51.6'
49.5'
45.0'
40.0'



4.56c
11.23c
29.75c
14.19c

S.OOc




LINE No. 10

Hole Y 55.0' 18.89c 27.5'
Hole 33 55.5' 18.89c 100'
Hole 34 49.5' 18.02c 200'
Hole 35 40.0' S.OOc 200'
20'

Width at top 547.5'
Width at bottom 500'

KEYSTONE CREEK PLACERS

(From actual drill records)

Key Chart to Estimate of Line 9 on Plate "B"; of Estimate of Line 10
on Plate "C"; of Block Estimate on Plate "D."

NOTE

Left limit of Line 9 determined by low value actual drill-hole. Right
limit of Line 9 determined by approximation of dredging limit and
marked by "fictitious" drill-hole "X."

Left limit Line 10 determined by some physical factor probably an
irregular rim. "Fictitious" Hole "Y." Right limit Line 10 determined
by too low value of Hole #35. Engineer has approximated limit of values
20 feet inside of this Hole and marks "fictitious" hole #35' giving it a
limiting value of 5^.



DRILLING FOR PLACER GOLD 77



PLATE "B"
KEYSTONE CREEK PLACERS Valuation of Line 9

Area of Square Cubic

Block Feet Yards Cents

A equals 49 5 2 x3 742.5 or 27.5 x 3.04 = 83.6

B equals 49 5&516 x 189 9553.9 or 353.8 x 7.89=2791.4

C equals 51 6 ^ 49 5 x 192 9705.6 or 359.5 x 20 49 = 7366.1

D equals 49 - 5 2 &45 x 197 9308. 2 or 344.8 x 21.97 = 7575.2

E equals 45 & 40 x 116 4930.0 or 182.6 x 9.59=1751.1

F equals 40 * 20 400.0 or 14.8 x 3.33 = 49.3



34640.2 1283.0 15.25 19616.7
One foot into bedrock 694.0

35334.2 1308.7 14.99 19616.7

NOTES

There is given to Areas "A" and "F" a value equal to only two thirds
of their governing drill-hole. These small areas are the approximation
of the departure from the vertical of the dredge bank.

Under the "Cents" column is the average value of the two bounding
drill holes.

To the yardage total has been added the barren material resulting
from dredging one foot into bedrock.

The figure 14.99 represents the value in cents per cu. yd. of the line
and is gained by dividing 19616 . 7 by 1308 . 7.



78 DRILLING FOR PLACER GOLD



PLATE "C 1



KEYSTONE CREEK PLACERS Valuation of Line 10

Area of Square Cubic

Block Feet Yards Cents

A equals 55x 2 27 ' 5 756 or 28.0 x 12.59 = 352.5

B equals 55 & 2 55 5 x 100 5525 or 204.6 x 18.89 =3864.9

C equals 55 5 ^ 49 5 x 200 10500 or 389.0 x 18.46 = 7180.9

40 'i flr 4ft

D equals x 200 8950 or 331.5 x 11.51 =3815.5

E equals 40 * 20 400 or 14.9 x 3.33 = 49.7



26131 968.0 15.72 15263.5
One foot into bedrock 500 18.4

26631 986.4 15.48 15263.5

NOTES

See Notes on Plate "B."

The figure 15 .48 represents the value in cents per cu. yd. of the line
and is gained by dividing 15263 . 5 by 986 . 4.



DRILLING FOR PLACER GOLD



PLATE "D"

KEYSTONE GREEK PLACERS
Estimate Gross Value of Block Between Lines 9 and 10

Area of Projected Gross Cubic

Section Area Value Yards

Line 10 = 26131 x .9925 (Cos. 7)= 25935 15263.5 968
Line 9 = 34640.2 x .9563 (Cos. 17) = 33126 19616.7 1283

2)59061 34880.2 2251

29530.5

29530.5 (Average area projected base) multiplied by 945 (Surveyed or
plotted distance between middle of both lines which is altitude of
"block") gives a total cubic content of 27,906,522 Cubic Feet.
27,906,522 Cu. Ft. equals 1,033,367 Cu. Yds.

The Gross Value Factor, divided by Cu. Yds. Factor equals:
2251 )34880 . 2 ( 1 5 . 49 cents Value of block

Total Value of Block equals 1,033,367 times 15.49 or $160,099.70.

As a check on Calculations we may figure the same Total by using the
products of the Line Calculations after adding "One Foot Into Bedrock."

Area of
Section

Line 10= 986.4 Cu. Yds. x .9925 (Cos. 7)= 979.0
Line 9 = 1308.7 Cu. Yds. x .9563 (Cos. 17) = 1251.5

2)2230.5

1115.25
1115.25 x 945 = 1,053,911 Cu. Yds.

Total Value of Block equals 1,053,911 x 15.19c = $160,089.08.

NOTE

A line is drawn connecting the centre of the Lines 9 and 10. These
lines are then projected so as to form a 90 angle with this "altitude"
line. The projected base areas are added, averaged, and multiplied by
the altitude to find content of block in Cu. Yds. Additions and sub-
tractions might have been made for irregular rim.



DRILLING FOR PLACER GOLD



PLATE "'



CORE MEASUREMENTS KEYSTONE PLACERS

Total

Core Measured on Surface Cubic

Core Measured in Pipe Without Slimes With Slimes Feet

as per



Hole Depth Drive


Total


Per Ft.


Total


Total


Average Total


Average Const.


No.


Ft.


Ft.


Ins.


Ins.


Cu. Ft.


Cu. Ft.


Cu. Ft.


Cu.


Ft.


Cu. Ft.


.27


1


110


110


1446


14.32


21.69


30.27


.2752


(Not


Measured)


29.70


2


105


98.5


1539


15.83


23.08


25.18


.2556


39


.53


.401


26.60


3


105


98.5


1521


15.44


22.82


26.30


.2669


37


.80


.384


26.60


4


105


97.6


1477


15.14


22.16


24.87


.2547


38


.82


.398


26.35


5


105


96.1


1600


16.65


24.00


26.33


.2740


38


.02


.396


25.95


6


105


97.4


1493


15.33


22.40


24.35


.2499


36


.00


.369


26.30



7 107 99.7 1529 15.34 22.94 22.36 .2243 28.75



288 26.91



8 98.5 83.0 1402 16.90 21.03 25.24 .3041 32.30 .389 22.41



840.5



12007 15.34 180.12 204.90 .2621 251.22 .3746 210.81



NOTES

Figures under "Depth" represent total from surface under "Drive" they represent
actual drilling. (Holes were started in a pit.)

This Chart, taken from the Report of an Engineer, was prepared by him that he might
compare the core records of various similar holes. It shows work that is reasonably
uniform, with no outstanding discrepancies, and proves that the material actually re-
covered, if discounted for the "swelling" of the gravels, checks very closely with the
theoretical displacement of the drive-shoe.



DRILLING FOR PLACER GOLD



81



PLATE "F"

KEYSTONE DRILLER COMPANY
TABLE FOR FINDING VALUE PER CUBIC YARD

(When depth of drill-hole and weight of

gold in milligrams are known)

CONSTANT .27



Depth to




Depth to




Depth to




Bedrock in




Bedrock in




Bedrock in




Feet


Factor


Feet


Factor


Feet


Factor


10


.6000


26.5


.2264


43


.1395


10.5


.5714


27


.2222


43.5


.1379


11


.5455


27.5


.2182


44


.1364


11.5


.5217


28


.2143


44.5


.1348


12


.5000


28.5


.2105


45


.1333


12.5


.4800


29


. 2069


45.5


.1319


13


.4616


29.5


.2034


46


.1305


13.5


.4444


30


.2000


46.5


.1290


14


.4286


30.5


.1967


47


.1277


14.5


.4138


31


.1935


47.5


.1263


15


.4000


31.5


.1905


48


.1250


15.5


3871


32


.1875


48.5


.1237


16


.3750


32.5


.1846


49


.1224


16.5


.3636


33


.1818


49.5


.1212


17


.3529


33.5


.1791


50 '


.1200


17.5


.3429


34


.1765


50.5


.1188


18


.3333


34.5


.1739


51


.1177


18.5


.3243


35


.1714


51.5


.1165


19


.3158


35.5


.1690


52


.1154


19 5


.3077


36


.1667


52.5


.1143


20


.3000


36.5


.1644


53


.1132


20.5


.2927


37


.1622


53.5


.1121


21


.2857


37.5


.1600


54


.1111


21.5


.2791


38


.1579


54.5


.1101


22


.2727


38.5


.1559


55


.1091


22.5


.2667


39


.1539


55.5


.1081


23


.2609


39.5


.1519


56


.1071


23.5


.2553


40


.1500


56.5


.1062


24


.2500


40 5


.1481


57


.1053


24.5


.2449


41


.1463


57.5


.1044


25


.2400


41.5


.1446


58


.1035


25.5


.2353


42


.1429


58.5


.1026


26


.2308


42.5


.1412


59


.1017



Diameter of Cutting -Shoe 7>2 inches. Value of gold 0.06 cents per milligram
$18.66 per ounce. To find value in cents per cubic yard, multiply number of milligrams
of gold recovered from drill-hole by the factor in the table opposite the depth to bedrock



82



DRILLING FOR PLACER GOLD



PLATE "G"

KEYSTONE DRILLER COMPANY
TABLE FOR FINDING VALUE PER CUBIC YARD

(When depth of drill-hole and weight of

gold in milligrams are known)

CONSTANT .3068



Depth to




Depth to




Depth to




Bedrock in




Bedrock in




Bedrock in




Feet


Factor


Feet


Factor


Feet


Factor


10


.5280


26.5


.1992


43


.1228


10.5


.5029


27


.1955


43.5


.1214


11


.4800


27.5


.1920


44


.1200


11.5


.4591


28


.1886


44.5


.1187


12


.4400


28.5


.1853


45


.1173


12.5


.4224


29


.1821


45.5


.1160


13


.4061


29.5


.1789


46


.1148


13.5


.3911


30


.1760


46.5


.1136


14


.3771


30.5


.1731


47


.1123


14.5


.3641


31


.1703


47.5


.1112


15


.3520


21.5


.1676


48


.1100


15.5


.3407


32


.1650


48.5


.1089


16


.3300


32.5


.1625


49


.1078


16.5


.3200


33


.1600


49.5


.1067


17


.3106


33.5


.1576


50


.1056


17.5


.3017


34


.1553


50.5


.1046


18


.2933


34.5


.1530


51


.1035


18.5


. 2854


35


.1509


51.5


.1025


19


.2779


35.5


.1487


52


.1015


19.5


.2707


36


.1467


52.5


.1006


20


.2640


36.5


.1447


53


.0996


20.5


.2575


37


.1427


53.5


.0987


21


.2514


37.5


.1408


54


.0978


21.5


.2456


38


.1389


54.5


.0969


22


.2400


38.5


.1371


55


.0960


22.5


.2347


39


.1354


55.5


.0951


23


.2296


39.5


.1337


56


.0943


23.5


.2247


40


.1320


56.5


.0935


24


.2200


40.5


.1304


57


.0926


24.5


.2155


41


.1288


57.5


.0918


25


.2112


41.5


.1272


58


.0910


25.5


.2071


42


.1257


58.5


.0903


26


.2031


42.5


.1242


59


.0895



Diameter of Cutting-Shoe 1Y^ inches. Value of gold 0.06 cents per milligram
$18.66 per ounce. To find value in cents per cubic yard, multiply number of milligrams
of gold recovered from drill-hole by the factor in the table opposite the depth to bedrock.



DRILLING FOR PLACER GOLD



83



PLATE "H"

KEYSTONE DRILLER COMPANY
TABLE FOR FINDING VALUE PER CUBIC YARD

(When depth of drill-hole and weight of
gold in milligrams are known)
CONSTANT



Depth to




Depth to




Depth to




Bedrock in




Bedrock in




Bedrock in




Feet


Factor


Feet


Factor


Feet


Factor


10


.4860


26.5


.1834


43


.1130


10.5


.4629


27


.1800


43.5


.1117


11


.4418


27.5


.1767


44


.1105


11.5


.4226


28


.1736


44.5


.1092


12


.4050


28.5


.1705


45


.1080


12.5


.3888


29


.1676


45.5


.1069


13


.3738


29.5


.1647


46


.1057


13.5


.3600


30


.1620


46.5


.1045


14


.3471


30.5


.1593


47


.1034


14.5


.3351


31


.1568


47.5


.1023


15


.3240


31.5


.1543


48


.1013


15.5


.3135


32


.1518


48.5


.1002


16


.3037


32.5


.1495


49


.0992


16.5


.2945


33


.1472


49.5


.0982


17


.2895


33.5


.1450


50


.0972


17.5


.2777


34


.1429


50.5


.0963


18


.2700


34.5


.1408


51


.0953


18.5


.2627


35


.1388


51.5


.0944


19


.2558


35.5


.1369


52


.0935


19.5


.2492


36


.1350


52.5


.0925


20


.2430


36.5


.1331


53


.0917


20.5


.2371


37


.1313


53.5


.0909


21


.2314


37.5


.1296


54


.0900


21.5


.2260


38


.1279


54.5


.0892


22


.2209


38.5


.1262


55


.0884


22.5


.2160


39


.1246


55.5


.0876


23


.2113


39.5


.1230


56


.0868


23.5


.2068


40


.1215


56.5


.0860


24


.2025


40.5


.1200


57


.0853


24.5


.1984


41


.1185


57.5


.0845


25


.1944


41.5


.1171


58


.0838


25.5


.1906


42


.1157


58.5


.0831


26


.1869


42.5


.1143


59


.0824



Diameter of Cutting-Shoe 7M> inches. Value of gold 0.06 cents per milligram
$18.66 per ounce. To find value in cents per cubic yard, multiply number of milligrams
of gold recovered from drill-hole by the factor in the table opposite the depth to bedrock.



84 DRILLING FOR PLACER GOLD



PLATE "I"
KEYSTONE DRILLER COMPANY

GOLD DREDGE CAPACITY CHART

Cubic Yards Elevated per Month of 30 Days at
Various Efficiencies for Different Sizes
(Bucket Speed at 50 Feet per Minute)

Figures are based on an actual operating time of 20 hours out of
each 24.

Size of Dredge 100% Efficiency 80% Efficiency 60% Efficiency

2^Cu.Ft. 89,000 71,000 53,000

3^ Cu. Ft. 108,000 . 86,000 65,000

5 Cu. Ft. 140,000 112,000 82,000

7^Cu.Ft. 182,000 146,000 110,000

9 Cu. Ft. 213,000 171,000 129,000

15 Cu. Ft. 304,000 244,000 184,000

From this table the Engineer may roughly approximate the yardage
of a proposed dredge once he knows the physical and climatic condi-
tions to be encountered and general working conditions.



DRILLING FOR PLACER GOLD



85




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