Idaho County free press. [volume] (Grangeville, Idaho Territory) 1886-current, 1896-02-28
THE FREE PRESS
0RANGEvILLE. IDAHO.
FRIDAY. FEBRUARY 2S. 1896
Hints in Regard to T'eiiMs'ides.

The following article on the
richest of all gold ores, now found
in such abundance in Cripple
Creek and other mining districts,
was written for the Mining and
Scientific Press by DR.. Richard
Pearce, manager Of the Boston and
Colorado Smelling Co:
"At the present time, owing to
the discovery of gold in Cripple
Creek in combination with tellu-
rum, prospectors are on the search
for similar conditions in other dis
tricts, and it has occurred to me
that few hints in regard to tel
lurides might be ofsome value.
"Tellurides proper are rarely
found to exist near the surface of
lodes that may contain them in
depth. This is due to the fact that
tellurium is susceptible to oxidiz-
ing action like iron pyrites and
other minerals when they are ex-
posed to weathering influences.
This weathering action, in the case
of tellurides has the effect of con-
verting the tellurium into an oxidiz-
ed form, which combines..with oxide
Ofiron and seldom shows any evil
dence of it's existence, except in
rare cases, when the ore is exceed
ingly rich, and then the oxide of
tellurium appears as yellowish-
brown stain on the rock.
"The gold resulting from the
Oxidizing change occurs as a brown
ish powder, and does not possess
the properties of gold found under
other conditions. 1t has little or
no lustre, and is so light in weight
and spongy that the ordinary pro-
cess of panning fails in most in
stances to indicate its existence.
The ordinary method of assay will
however, prove it's presence, and
this should be done by some as
sayer who is not only qualified by
experience to make the assay, but
whose honesty is beyond question.
Prospectors will do we'll to give a
wide berth to the quack assayer
who has some particular method
of his own, or what he pleases to
call arr'chemical analysis process,
which he claims is the only true
method for determining the value
Of an ore.
"It sometimes happens that a
prospector is SO far away from a
reliable assayer that it is impossi-
BILE for him to ascertain whether
the ore contains gold or not when
the presence Of tellurium is sus-
pected.
"a very simple test, requiring
no particular skill, can be used to
determine whether or not tellurium
is present in the oxidized form; for
If it is found that tellurium is pres
ent, it is pretty safe to assume that
gold accompanies it. The test,
which l will give here, is one
which l recommended in paper
read before the Colorado Scientific
Society some two years ago, and
was the result of some investiga.
tons on oxidized Cripple Greek
ores.
Fifty grammes of the fine pulp
ore treated with dilute hydro
chloric acid, consisting of equal
parts Of sacid and water. The
mixture is heated to boiling and
filtered, and to the filtrate is ad-
ded solution of stannous chloride.
The tellurium, If present, will i'm
mediately be precipitated in
black, foculent form as metallic
tellurium. If it's quality is small
it Is better to heat the solution,
which aids the separation. 1t
must however, be remembered that
this test is only applicable to ores
which contain the tellurium in an
Oxidized form, and is of no value
in other cases.
s'Below the water line in the
tellurides proper occur, and in
Cripple Creek they are represented
by the minerals sylvanite and Gala
verite. Sylvanite is as white and
lustrOus as pure silver, and con-
tains, when pure, about twenty
seven per cent. gold. Calaverite
has a slight yellow appearance, re-
sembling somewhat pale variety
of iron pyrites, and contains about
forty per cent. of gold.
1.-The presence of tellurium does
not in every case prove the exis-
tence Of gold, but think 1t may
be said to be the rule in Cripple |
Creek. Boulder county has. pro-
duoed what is termed native tellu-
rum and telluride of lead (altaite)
which contains no gold whatever,
and l have known ofno occurrence
Of telluride of bismuth (tetrady-
mite) in Montana, containing little
Or no gold, but these examples are
rare. The occurrence of fluorite
II q purple or amethystine color,