Year: 1888

page_text: hereby declare the nature of this invention to be as follows:-
The object of the present improvement is to provide means of rendering fit for
amalgamation such auriferous and auroargentiferous ores that have resisted all processes
hitherto proposed to that effect.
It has been ascertained that 'certain classes of pyritous ores and especially auriferous
mispickels cannot be successfully treated by the process of direct amalgamation
described by me in my original "Patent nor in fact by any other process of amalga-
mation.
Now the present improvement consists, when the ores are of a silicious character,
in roasting and melting them in combination with some alkaline substance and a
small quantity of charcoal. When the fusion has been thus effected the product
obtained is found when ground to amalgamate as readily as may be desired.
The alkaline substance which I prefer in practice for the said purpose is the carbonate
of soda which has the advantage of its low cost and easy fusion. I do not wish
however to limit myself to the use of the said imaterial as others may be equally used
but with less advantage. The proportion 1 value approximately to 10 to 30 per cent.
of the matter in treatment; it will be necessary for determining the exact proportion
in each case to consider the nature of the gangue of the ore and also the proportion
of precious metals held by it. The more soda is used and the quicker the action takes
place, also the less heat is required for the fusion; but increase of cost opposes to their
being used more than is strictly required, particularly when the tenure in precious
metals is not large. The proportion of soda to be used will have consequently to vary
materially according to circumstances. It is important however to bear in mind that
no less than 8 or 10 per cent. should be used, as otherwise the formation of fluid glass
produced by the combination of soda with the silicious compounds and with the metals
left in the state of oxides after the roasting which frees the precious metals and fits
them for ready amalgamation could only be effected at very high temperatures difficult
to be obtained in practice.

page_text: The addition of charcoal will have to vary from 0.4 to 0.8 per cent. of ore to be
treated according to requirement, the object of this addition being to assist in the
reduction of the oxides and the freeing of the precious metals:
24
When the ore is not or is insufficiently silicious it is found necessary to add to it.
quartz in a proportion varying according to requirement, from 75 to 100
per cent.
of the mass under treatment in order to allow the action of the soda to take
place.
Whatever may be the composition of said fluid glass, the precious metals will benefit
by the presence of the alkaline addition being thus freed from their combinations with
sulphur, arsenic, antimony and other similar substances.
The above process may be carried on in stoves of a similar style to those used in
the manufacture of soda which are well known and need not be described.
.
If suitably managed the above process will yield as inuch as 98 per cent. of the
precious metals contained in the gangue.
I wish it to be well understood that the addition of soda is specially meant here, with
the assistance of silica, to form silicates which search out and absorb the inferior metals
and metalloids so as to free the precious metals for amalgamation.
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Improvements in Treating Auriferous and Auroargentiferous Ores.
1, JULES WEIRICH of Beziers, Herault, in the Republic of France, Engineer, 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:-
:
It has been found that many auriferous minerals of a very complicated composition,
such as the auriferous mispickles, gallenas, blends, fablerz, in which gold appears to be
combined with arsenic, sulphur and antimony and even directly with ordinary metals,
cannot be treated with success by the ordinary process of amalgamation even" after
having been submitted to a preliminary heating in a lead bath, as indicated in niy
former patent No: 7657 in the year 1887.
1 have found that by fusing the pulverised mineral, after a preliminary roasting,
withlan alkaline carbonate either by preference, carbonate of soda or a mixture of
carbonate of soda and of carbonate of lime in presence with a small, proportion-of
carbon, vitreous compound silicates are finally obtained into the composition of which
all the ordinary metals contained in the mineral treated enter; the preliminary
roasting having for its effect to get rid of the greater part of the sulphur, arsenic,
antimony, tellarium &c. and the fusion setting the precious metals at liberty, and
principally the gold, which is found distributed in a free state amongst the
gangue.
With this end my invention consists in a new process for. the treatment of
auriferous or auroargentiferous minerals to prepare them for amalgamation as described
above.
In the application of my process I mix with the pulverised and previously roasted
minerals an alkaline carbonate, for example, carbonate of lime, carbon and quartz, if
the mineral does not contain sufficient of this last, a certain proportion of quartz
being necessary for the formation of the vitreous mass.. The whole is then melted in
an ordinary. alkaline melting furnace or in a pot furnace such'as is'employed in the
manufacture of glass. It is especially important to obtain the temperature necessary
for fusion which permits the chemical reactions indicated above to take place. If the
treatment is carried on with care the loss of gold is extremely small.
The product of the fusion-is-then-ground or reduced in any other manner to the
state of powder and the precious metal is obtained from it by the ordinary process of
amalgamation.
It will be remarked that the fusion of the roasted mineral is not intended to obtain
the metal in the state of regulus but simply to disengage the precious metal from the
metallic and metalloid constituents of the mineral and of the gangue so as to allow it
to amalgamate freely.
In practice, for the sake of economy I employ carbonate of soda which has also the
advantage of melting more easily than any other alkaline salt. The carbonate of sodą
is in the proportion of 10 to 30 per cent. of the mineral to be treated. This proportion
will vary according to the nature of the gangue of the mineral and with the quantity
of precious metal which is contained in it.

page_text: The reaction takes place so much the better if more soda be employed. The more
there is of soda the less heat is necessary for the fusion. If the mineral is poor in
metal it is necessary to limit the quantity of soda to be employed in order that the
treatment may be commercially possible. In consequence, as I have stated, the
proportion of soda varies with the different minerals, but in no case should it be smaller
than eight to ten per cent. for otherwise the formation of the glass or silicate of, soda
resulting from the combination of the soda with the silicious components and the
metals which are found in the state of oxide after the roasting will not be effected
except at a very high temperature difficult to obtain in practice.
The wood charcoal will vary from 0.4 to 0.8 per cent. of the mineral under .treat-
ment its presence will cause a partial reduction of the oxides and the liberation of
the precious metals.
In case the minerals are not contained in a silicious state gangue it will be
indispensable, in order to obtain a fusion to anything like a homogeneous state to add
to them quartz in a proportion sufficient to render fusion with carbonate of soda
possible..
Whatever however may be the composition of the glass, the precious metals combined
with the mineral are disengaged from their combinations with sulphur, arsenic,
antimony and other analogous bodies.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The process above described for the preparation of auriferous and auroargenti-
ferous minerals which consist, firstly, in roasting the mineral; secondly, in mixing it
with carbonate of soda and carbon or carbonate of soda and carbonate of lime and
carbon; and thirdly, in submitting it to a heat sufficient to form compound silicates
substantially as I have described in the present specification.
2. The process above described for the preparation of auriferous and auroargenti-
ferous minerals which consists; firstly, in roasting the mineral; secondly, in mixing it
with carbonate of soda and carbon or carbonate of soda and carbonate of lime and
carbon and in each case with quartz if the mineral does not contain sufficient; and
thirdly, in submitting it to a heat sufficient to form compound silicates substantially as
1 have described in the present specification.
3. The process described above for the preparation of auriferous and auroargenti-
ferous minerals for amalgamation which consists; firstly, in roasting the mineral, then
in mixing with the mineral one or more of the alkaline carbonates and carbon and
quartz, if this be necessary, then in melting the mixture to form compound silicates,
and finally, in reducing the mass to a state of powder for amalgamation substantially
as I have described in the present specification.
Dated this 17th day of January 1889.