Improvements in Mining Gold and similar Metals.
Year: 1896

page_text: Date of Application, 4th Aug., 1896-Accepted, 5th Sept., 1896
COMPLETE SPECIFICATION.
Improvements in Mining Gold and similar Metals.
1, HERMAN FRASCH of Euclid Avenue, corner of Kennard Street, in the City
of Cleveland, in the County of Cuyahoga and State of Ohio, one of the United
States of America, Manufacturer, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
This invention relates more particularly to the recovery of gold from placer
deposits which either contain the gold in too small quantity for working by the
methods heretofore known or used, or which from lack of water or peculiarity of
location are not workable (at least profitably) by said prior methods.
It may, however, be applied to the recovery of gold from other porous or
permeable deposits, and to the recovery from such deposits of analogous metal
(silver or platinum for example); and it is generally to be understood that each of
the improvements constituting the said invention is intended to be secured for all
the uses to which may be applicable.
In accordance with said invention, a reagent which converts the naturally
insoluble gold or analogous metal into a compound or compounds soluble in water is
introduced into the porous or permeable auriferous (or analogously metalliferous)
earth, which is generally sand or gravel, as it lies in its natural bed in the ground;
the aqueous solution of gold (or the like) formed by the aid of such reagent, is
removed by any, known or suitable means for conveying liquids, such as pumping or
the like, including drainage, (if the situation admit of it), and the gold (or like
metal) is recovered from the solution by known or suitable means for recovering
metal from solution, such as chemical precipitation, electrical deposition, or the like.
Where the earth contains other like metal as well as gold, these may be mined
together by using a reagent which converts both into soluble compounds, or they
can be mined separately by using in succession reagents of which each renders one
of the metals soluble.
In the introduction of the reagent which renders the gold (or like metal)
soluble, hydrostatic columns, pumps or other pressure-applying means may be used
to force the reagent into the earth, or reliance may be had (when the earth is
sufficiently permeable) upon gravity alone. Practically the use of pressure is
important and is specially claimed.
The reagent employed may he any known or suitable substance or combination
of substances for forming solable compounds with gold (or like metal), such as
chlorine and bromine, for gold, the alkaline hyposulphites for silver, and potassium
cyanide for gold or silver or both. Chlorine may be advantageously used for
platinum. This is often present with gold, and can be mined with it, by means of
chlorine.
These are given as illustrations; other reagents may be used. In using a
combination of substances, they may be used in admixture, or in succession. An
example of the successive use of substances would be the formation of silver
chloride by the introduction of chlorine, and the making of this silver chloride
soluble in water by means of sodium hyposulphite.
It is most advantageous to use the reagent in aqueous solution; such solution
being introduced into the auriferous or argentiferous or platiniferous earth in its
natural bed in the ground and allowed to remain for a suitable time in contact
therewith (in percolating or while standing). The more or less strong solution of
gold (or silver or platinum or two or more of them) is then withdrawn.

page_text: The gold and like metals are, as a general thing, distributed unequally through
placer deposits, the working of which is more particularly the object of the present
invention.
The gold, for example, in such deposits is as a rule mainly or almost wholly
in the lower part or near the bed rock. The reagent may be allowed to find its
way to the metal through overlying or intermediate masses of earth which are but
slightly or not at all auriferous (or argentiferous or platiniferous); but it is an
improvement to drive a well, shaft, ditch or tunnel to or near the auriferous (or
argentiferous or platiniferous) portion of the mass, and to introduce the reagent
more directly thereto by means of such well, shaft, ditch or tunnel. Practically
wells or shafts would be sunk or driven (at least in most cases) down to the bed of
the rock, so that the pit of the well or shaft is in the metalliferous earth.
Sometimes it may he desired to mine the metal from auriferous (or like) earth
which is so flooded with water as to interfere with the penetration or operation of
the reagent; in such cases it may be possible to drain off the excess of water; but
if this is not practicable, or it be preferred not to do so, a chemical solution (of a
suitably high specific gravity) may be introduced under the water-carrying earth
and be made to displace the water so that the reagent may enter and act upon the
gold (or like metal). A proper specific gravity of the chemical solution may be
obtained (at least in some cases) by the use of a sufficient quantity of reagent, (but
where this is too expensive or for any reason is not desirable), it may be secured
by additions of other substances, the most convenient substance being common salt
(sodium chloride).
As already indicated the reagent may act upon the gold (or like metal) in
percolating through the ground or while standing therein. To collect the metallic
solution formed in percolation, intercepting receptacles are provided at a suitable
depth having openings or outlets for giving access thereto. These receptacles may
be simply the pits at the bottom of wells sunk into the mine, or they may be
formed by open or covered ditches, or they may be formed in whole or in part by
artificial walls (vertical or horizontal) or they may be formed in other like ways.
To provide for the reagent standing in contact with the gold (or like metal) walls
may be built in the mine so as by themselves or in connection with the natural
rock to form chambers or basins enclosing the auriferous (or argentiferous or
platiniferous) earth, access for removal of the solution of gold or like metal being
given by shafts or other openings. These could serve also to introduce the
chemical solution, which might, however, be allowed to percolate into the basin.
In some cases artificial basin-forming walls may not be necessary, the reagent when
introduced into the ground standing sufficiently in consequence of the nature or
natural surroundings of the auriferous (or like) earth. In such case (as also in the
case of an artificially formed basin) the same pipe, well, shaft or tunnel may serve
to introduce the reagent which renders soluble the gold (or like metal) and to
remove the solution of gold (or like metal). The reagent can be applied to the
same earth and the metallic solution removed therefrom repeatedly, as often in
fact as a yield is obtained.
:
The mine to be treated in accordance with this invention is generally a deposit
in an excavation in solid rock, (such as the bed of an ancient river), and the inost
advantageous treatment (itself a special improvement) is to build one or more walls
at: intervals across the excavation or valley, (they extending from the bed rock
upward to the surface or to any desired distance above or below the same), and to
sink or drive a number of wells or shafts at intervals in the parcels of ground above
such walls.
As already stated it is an advantage and a 'special improvement to force the
reagent into the earth, it is also an advantage to exhaust the solution of gold (or
like metal) from the earth by the aid of a vacuum or diminution of pressure in the
earth around the well pit below the level of such solution.
In order to enable those skilled in the art better to understand and carry out
the invention, the following particular examples are given by way of illustration of

page_text: certain modes of practicing the invention, reference being had to the accompanying
drawings which form part of this specification and in which-
Figs. I and II are diagrams, respectively in plan and longitudinal section, of a
mine in an ancient river bed provided with artificial basin-forming walls and with
wells or shafts whose pits constitute intercepting receptacles;
Fig. III is a diagrain of the same mine in cross section on line i ii of Fig. I ;
Fig. IV is a diagram in vertical section of a hillside mine; and
Figs, V, VI and VII are diagrams of wells provided with pumping machinery
which may be used for introducing or forcing the reagent into the mine, or for
removing or exhausting and removing the solution of gold (or like metal), or for
both purposes.
Fig. VIII is a diagram showing the lower end of a reagent-introducing or
reagent-removing pipe on a larger scale than that of the other figs. and 'in
section.
Let it be assumed that the mine consists of auriferous sand and gravel A. and
overlying earth A which contains little or no gold;' deposited in the bed of an.
ancient river between the banks B, and that such deposit averages 20 feet in depth
and 200 feet in width; the dip of the bed rock C being 50 feet to the mile. These
figures substantially represent an actual case; the diagrams it will be understood
are not intended to preserve the proportion to one another of the different
dimensions. It will, of course, also be understood, that the dimensions and other
circumstances and their relations to one another are variable in reality. At
intervals of about half a mile or at greater or less intervals, trenches may be dug
across the valley down to the bed rock. These trenches are filled with cement
concrete forming solid impervious walls D with about half a mile (or more or less
as the case may be) of deposit between adjacent walls. These parcels of ground
would, of course, be the width of the valley across. In them, at say about 100 feet.
or at greater or less distances apart, wells E may be driven down to the bed rock
and provided with suitable pipes or casings or pipes and casings.
In Fig. V the well is shown provided with a pipe 2 which fits closely the bore
of the well, so that a vacuum can be maintained in the well pit, the surrounding:
earth forming a packing. The pipe is shown as resting on the bed rock and is
provided with perforations near its lower end. Preferably the pipe 2 is of iron
coated internally and externally with lead, although it may be of wood, or lead, or
any material of suitable strength able to resist or protected against corrosion by
the reagent. Near its upper end the pipe 2 is connected through a non-corrodible
pump 3 with a lead-lined or other non-corrodible tank 4, which latter is provided
with non-corrodible pipe line 5. The pump 3 removes the metallic solution from
the well and delivers it into the tank 4, to be thence discharged by the pipe 5.
The tauk 4 might also serve to receive the chemical reagent and the pump 3 to
withdraw it therefrom through a suitable connection with the bottom of the tank
and force it through the pipe 2 into the metalliferous earth A; or the reagent may
be introduced from any suitable source through the pipe 2 independent of the
pump; or part may be run in directly through the pipe 2 aud part be forced down
by the pump 3.
In Fig. VI the well' is provided like an oil well with a casing 2¹ to enclose the
pipe 2 and an underground pump (not represented) whose sucker rod 6 is shown
connected with one end of a walking beam 7, the opposite end being provided with
a chain or rope 8 that leads to an engine (not shown) for reciprocating it and the
sucker rod. The casing is perforated near the bottom. A packer is arranged
between the pipe and the casing at a point above the perforations, so that the
liquid cannot asceud past the packer. The pump raises the metallic solution and
delivers it through the pipe 2 into the tank 4 from which it may be discharged by
the pipe 5. For introducing the reagent the pump with its pipe and 'packer could
be removed and a pipe and packer inserted for introducing the reagent.
In Fig. VII the tank 4 has its bottom and top both connected with the pipe 2
and a branched pipe 9 with a valve in each branch leads to both the induction

page_text: and discharge sides of an air pump 10, so that air can be forced into the tank 4 or
be exhausted therefrom as the operator may determine. A stopper 11. for closing
the bottom opening when desired is indicated in dotted lines. By filling the tank 4
(through the pipe 5 or otherwise) and then compressing air into it by the pump 10
the reagent may be forced down the pipe 2 (the stopper 11 being raised and the
pipe 5 closed and the pipe 9 being in communication with the compression side of
the pump 10). By shutting the stopper 11 and putting the pipe 9 in commu-
nication with induction side of the air pump, a vacuum can be made in the tank 4
and the metallic solution made to rise through the pipes 2 and flow into the
tank 4. By opening the pipe 5 (the stopper 11 being shut) and causing the pump 10
to force air into tank 4 its contents may be discharged through the pipe 5.
The wells of Figs. I, II and III may each be equipped like the well of Fig. V
or VI or VII or in any other suitable way. The arrangements of Figs. V and VII
are intended for shallow wells as they raise the solution of gold (or like metal) by
vacuum; but the arrangement of Fig. VI could be used with wells of any depth.
A force pump could also be used at the botton of shallow wells. Other forms of
pumping or lifting apparatus could be used instead of piston pumps. When the
wells are only 20 feet deep they may be easily dug by hand; with drive pipes or
hydraulic wash pipes, almost any depth can be reached.
Assuming that gold is to be recovered, the reagent may be chlorine. This can
be conveniently prepared in solution by dissolving chloride of lime (bleaching
powder) in water and adding enough sulphuric acid to liberate the chlorine. The
use of about four pounds of the chloride of lime to a ton of water is recommended.
The solution can be used at once, or be first allowed to settle. It is introduced
into the auriferous earth through one or more of the wells, and may be introduced
in sufficient quantity to soak the auriferous earth in the entire basin formed by a
wall D. To do this the height of the wall D (on the basis of a dip of 50 feet to the
mile and half a mile between walls) would have to be 25 feet plus the depth of
the auriferous deposit at the upper end of the basin. If the walls were only a
quarter of a mile apart, their height might be 12 feet less with the same dip. "It
is not necessary, however, to fill the whole basin; the solution may be introduced
at one or more of the wells and be allowed or forced to percolate to others, from
which it could be pumped out. A continuous flow might in fact thus be maintained.
If the overlying earth A' is sufficiently impervious, the solution might be made to
flow out of a well by pressure of the solution in the stratum A. The solution
might simply be forced into the sand or gravel about a well, left there for a suitable
time, and then pumped out through the same shaft and even the same pipe, the
operation being repeated as often as desired until the yield ceases.
It is generally recommended to introduce the solution at the highest well, and
remove it at the lowest, or at one of the intermediate ones if it be sufficiently
charged with gold.
The solution may remain in contact with the gold-carrying deposits for hours,
days, weeks, months, or even years; weak solutions may, therefore, be used, and
the extraction can be continued until practical exhaustion of the gold. Any depth
can be worked. As placer deposits do not ordinarily, contain sulphides nor other
substances on which the chlorine would waste itself, loss from this cause would
usually not have to be taken into account. In some cases where organic matter
exists, a solution of cyanide of potassium can be used more advantageously. It
can be handled with iron pumps and iron tanks. Solutions of two-tenths of one
per cent. (or even one tenth) will answer. In using chlorine for gold, if there be
silver in the deposit, the chloride of silver formed thereby could be recovered by
means of hyposulphite solution. If there be platinum it would be recovered with
the gold by the chlorine.
When a sufficiently rapid percolation is obtained thereby, the solution may
simply be run into the wells; but when desired, it can be forced by pressure in
the wells to penetrate the surrounding earth.
The hillside mine in Fig. IV is provided at an elevated point with a reagent-

page_text: introducing opening F in the auriferous or like earth A and overlying deposit A
in the form of a ditch, and at a lower point with a cement wall D which extends-
from the bed rock C to and above the top of the ground at that point.
In the ground above the wall D and in proximity thereto is a well E, and
below it a ditch G which extends to bed rock C.
On introducing the reagent in aqueous solution into the ditch F by pumps,-
buckets, conduits or other like means, said solution flows down the hillside perco-
lating through the auriferous or like earth A, converting the gold or like metal
therein into a compound soluble in water, and dissolving the same. The wall D.
intercepts the metallic solution so formed, which can be removed through the well E
by the appliances of Figs. V, VI and VII, or by other like means. In some cases
gravity might force it to rise through the well pipe. Also, it might be drained off
through an opening at or near the bottom of the wall D into the ditch G ; from
which it might be lifted out by pumps or buckets or other liquid-lifting appliances.
Also the solution might be carried (if the situation permit) into a storage or treating-
vat at a lower level by drainage directly from the receptacle or basin above the
wall D, or from the ditch G. If desired the solution can be removed as fast as it.
percolates into the receptacle formed by the wall D; or it can be allowed to collect
therein and to stand in contact with the gold or like metal before it is removed.
Further the wall D and well E might be dispensed with, and the solution be
intercepted by the ditch G, to be removed by pumping, drainage or otherwise.
course also, the wall D might be used without the ditch, and without the well E,
if other suitable outlet be provided.
Of
After the gold solution has been obtained, the gold is recovered therefrom as
may be preferred. Electrical deposition is considered the most advantageous mode,
chlorine solution being regenerated while the gold is deposited. It is unnecessary.
to go into the details of an electric deposition, as those skilled in such matters will
understand how to apply it. So also, if chemical precipitation be preferred for the
recovery, those skilled in the art will understand how to apply it without further
instructions. The regenerated solution of chlorine could be introduced again into.
the auriferous earth. •
If an analogous metal, like silver or platinum, is to be mined instead of or along
with gold, the preceding description will suffice for skilled persons to accomplish the
formation in the ground of a solution of such metal as well as the removal thereof
from the ground, and the recovery of the metal from the solution, electrical
deposition and chemical precipitation being available, as when gold is mined alone..
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is-
1. The process of mining gold, or analogous metal such as silver or platinum, by
introducing into the auriferous or argentiferous or platiniferous earth in its natural
bed in the ground a reagent which converts such metal into a compound soluble in
water, and removing the aqueous solution of gold or like metal formed by the aid.
of such reagent; substantially as described.
2. The process of mining gold, or analogous metal, such as silver or platinum, by
introducing into the auriferous or argentiferous or platiniferous earth in its natural
bed in the ground a reagent which converts such metal into a compound soluble in
water, removing the aqueous solution of gold or like metal formed by the aid of
such reagent, and recovering the metal therefrom; substantially as described.
3. The process of mining gold, or analogous metal, such as silver or platinum, by
forcing under pressure into the auriferous or argentiferous or platiniferous earth in
its natural bed in the ground a reagent which couverts said metal into a compound:
soluble in water, and removing the aqueous solution of gold or like metal formed
by the aid of such reagent; substantially as described.
4. The process of mining gold, or analogous metal, such as silver or platinum, by
introducing into the auriferous or argentiferous or platiniferous earth in its natural.

page_text: bed in the ground an aqueous solution of a reagent which converts such metal into
a compound soluble in water, and removing the aqueous solution of gold or like
metal formed by the aid of such reagent; substantially as described.
5. The process of mining gold, or analogous metal, such as silver or platinum, by
driving a well, shaft or opening in the ground through overlying or intermediate
masses to, into, or through the auriferous or argentiferous or platiniferous earth or
its vicinity, introducing into such earth through such well, shaft or opening,
a reagent which converts such metal into a compound soluble in water, and
removing the aqueous solution of gold or like metal formed by the aid of such
reagent; substantially as described.
6. The process of mining gold, or analogous metal, such as silver or platinum, by
introducing into the auriferous or argentiferous or platiniferous earth in its natural
bed in the ground an aqueous solution of a reagent which converts such metal into
a compound soluble in water, such solution being of a high specific gravity, and so
introduced as to displace water which the said earth may carry, and removing the
aqueous solution of gold or like metal formed by the aid of such reagent;
substantially as described.
7. The process of mining gold, or analogous metal, such as silver or platinum, by
introducing into the auriferous or argentiferous or platiniferous earth in its natural
bed in the ground a reagent which couverts such metal into a compound soluble in
water, causing such reagent in solution to percolate through such earth from its
point of introduction to one or more intercepting receptacles, and removing the
aqueous solution of gold or like metal formed by the aid of such reagent;
substantially as described.
8. The process of mining gold, or analogous metal, such as silver or platinum, by
driving a well, shaft or opening in the ground through overlying or intermediate
masses to, into, or through the auriferous or argentiferous or platiniferous carth or
its vicinity, introducing into such earth through such well, shaft or opening, a
reagent which converts such metal into a compound soluble in water, causing such
reagent in solution to percolate through such earth, and removing the solution of
gold or like metal from one or more intercepting receptacles through other wells,
shafts or openings; substantially as described.
9. The process of mining gold, or analogous metal, such as silver or platinum, by
enclosing the auriferous or argentiferous or platiniferous earth in its natural bed in
the ground in one or more artificially formed basins, introducing into such basins a
reagent which converts such metal into a compound soluble in water, and removing
the aqueous solution of gold or like metal formed by the aid of such reagent ;
substantially as described.
10. The process of mining gold, or analogous metal, such as silver or platinum,
by enclosing the auriferous or argentiferous or platiniferous earth in its natural
bed in the ground in one or more artificially formed basins, driving one or more
wells, shafts or openings into the earth in such basins or the vicinity thereof;
introducing into the basins a reagent which converts such metal into a compound
soluble in water, and removing the aqueous solution of gold or like metal formed
by the aid of such reagent; substantially as described..
11. The process of mining gold or platinum, by introducing a solution of
chlorine into the auriferous or platiniferous earth in its natural bed in the ground,
and removing the chloride of gold or platinum solution formed thereby; substantially
as described.
12. The process of mining gold or platinum, by introducing a solution of
chlorine into the auriferous or platiniferous earth in its natural bed in the ground,
removing the chloride of gold or platinum solution formed thereby, and recovering
the gold or platinum by electrical deposit; substantially as described.
13. The process of mining gold or platinum, by introducing a solution of
chlorine into the auriferous or platiniferous earth in its natural bed in the ground,
removing the chloride of gold or platinum solution formed thereby, recovering the
gold or platinum and regenerating the chlorine solution by electrical deposit, and

page_text: introducing such regenerated solution into the ground for acting again upon the
gold or platinum to effect its removal in solution; substantially as described.
14. A mine of gold, or analogous metal, such as silver or platinum, composed
of one or more wells, shafts or openings in the ground to, into, or through the
permeable auriferous or argentiferous or platiniferous earth or the vicinity thereof,
and provided with means, such as pumping machinery or the like, for introducing
or forcing a fluid reagent into the said earth, and for removing or exhausting and
removing the gold or silver os platinum solution; substantially as described.
15. A mine of gold, or analogous metal, such as silver or platinum, composed
of a basin with an artificially formed wall or walls enclosing auriferous or
argentiferous or platiniferous earth in its natural bed in the ground, with one or
more wells, shafts or openings into said basin, and provided with means, such as
pumping machinery or the like, for introducing or forcing a fluid reagent into the
earth in said basin and for removing or exhausting and removing the gold or silver
or platinum solution from the said basin; substantially as described.
16. A mine of gold, or analogous metal, such as silver or platinum, composed
of one or more reagent-introducing wells, shafts or openings in the ground on one
side of the permeable auriferous or argentiferous or platiniferous earth, and on the
other side thereof one or more intercepting receptacles having openings to give
access to such receptacles, said mine being further provided with means for
introducing the chemical reagent and removing the solution of gold or analogous
metal; substantially as described.
17. A mine of gold, or analogous metal, such as silver or platinum, composed of
a deposit of auriferous or like earth in a natural excavation like a river bed, and
provided with one or more basin-forming walls across the excavation or valley and
also with one or more wells or shafts in the parcels of ground above such walls;
substantially as described.
18. The process of mining gold, or analogous metal, such as silver or platinum,
by introducing into a natural body of permeable auriferous or argentiferous or
platiniferous earth in its natural bed in the ground a reagent which converts such
metal into a compound soluble in water, so that the said earth is permeated by
said reagent percolating through or standing in the said earth and the particles of
gold distributed through said earth are thus exposed to said reagent, removing the
compound thus formed in dilute aqueous solution, and recovering the metal
therefrom; substantially as described.
Dated this Second day of July 1896.
HERMAN FRASCH.