Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1907-05-25
SOME EXPERIENCES IN AS
SAYING TELLURIDE ORES
BY ]. N. MCLEOD.

experience in assaying of Colorado ores.
lie has devoted especial attention to the
testing of telluride ores, and is well
qualified to discuss the important sub
Ject. He is manager Of the Denver
(Colo,) Analytical and Assaying Com
pany.-Editor.
1t has long seemed to the writer that
too little is known regarding the losses
in the assay of telluride ores, and while
the following notes may cover ground
that has been more thoroughly gone
over by other assayers who may have
worked out method of testing to their
satisfaction, yet feels justified in pub
fishing them for several reasons.
In the first place, in mentioning to
some assayers of wide reputation, the
results the writer obtained, he has found
that they were new to them. Second
he has been unable to find data publish
ed along this line, which deals with any
thing excepting ores of low percentages
or of simple nature. For instance, the
work done by Hilebrand and Allen of
the United States Geological Survey
while of great value, deals with few
ores of comparatively simple compost
ton carrying little silver. The ores test
ed by the writer contained in every case
either high percentages of tellurium, or
tellurium with other metals, which ap.
parently had marked effect on the re-
suits in assaying.
Ore No. This sample was brought
to the writer some seven years ago, with
instructions to assay for gold. The ore
was of lead gray color, metallic luster,
and free from quartz or gangue of any
kind. Tellurium was at once suspected,
and it presence was determined by the
sulphuric acid test. 1t was also noted
that sulphur was present, and little
later, bismuth was detected.
The sample was prepared as usual, and
| charged into crucibes with heavy lith-
arge tlux such as was in common use on
Cripple Creek ores. Owing to the small
amount of pulp at hand, only / assay
| ton charges were used, Silver was add
ed. Resulting lead button was slightly
brittle, but not enough so to be consid-
cred detrimental. On cupelling no but.
ton was found Another charge was
made up, more litharge and a larger
piece of silver foil added. Still no but
ton. The cupel was then ground up and
assayed Result, no button, The cupel
was run again, and this time very
small button was obtained.
By this time it was thought best to call
on some one of greater experience and
II. v Furman, author of book on rs.
saying was consulted. Prof Furman
was greatly interested, and advised
combination method, consisting of treat
ment with nitric acid to oxidize the tel
lurium, precipitation of the silver with
sodium chloride, and scorifcation of the
residue for gold.
This was followed out with the aston
ishing result of some 80 ozs. of gold, and
5000 ozs. of silver per ton. The button
was found to be pure silver. The sam
pie was then submitted by Prof Fur
man to mineralogist of Denver, who
| classified it as an un named mineral
pho-tellurde of bismuth. This gen.
| tleman stated that he had recently had
| a sample of the same ore and advised
| the same treatment for it as already
used, adding that the precaution must
be taken to precipitate the silver with
salt and not hydrochloric acid, as other
wise combination would take place be-
tween the acid and the tellurium and
! redissolve the silver. Owing to lack of
ore no further tests were made on this
ore.
Conclusions these tests and
others, the writer is inclined to believe
that all telluride ores will not yield their
values to the same treatment. Astraight
telluride ore, even of high percentage,
will apparently give good results by the
scorification method, but where other
metals, such as bismuth or selenium are
present, it fails to work well. The com
bination method should yield good re-
suits if properly carried out.
The presence of other metals than gold
and silver in the button in the cupel is
something that was new to the writer
and not generally known. He has
thoroughly satisfied himself that bis
muth at least will be retained by the
silver. The mos, important feature o.
the results is that some of the ore tested
was considered of no value, and if tested
by the ordinary crucible method with
the usual flux for sulphide ore woulC
give no button Is it not possible tha
some good bodies of ore have been over
looked because the camp assayer report
ed in all good faith that the ore carried
no values