The Idaho Springs siftings-news., 1910-10-15
Zinc In Colorado Ores.

!
/ terial some attention and perhaps may
be the means of beneftting some of our
mine owners. A representative of this
paper was in Leadvills few days ago
and found the mining people very much
interested over what has formerly been
regarded as simply waste matter and
look forward to reaping rich harv est
from mining the discarded stuff Hence
in giving space to this report from the
School of Mines, it is with the feeling
that there may be similar valuable stuff
that IS being overlooked in this camp
| and a description of the peculiar zinc
ores may be of some advan tage:
he newly discovered material is re-
ported to have been found in many
mines; it appears to be most plentiful
near the parting quartzte, but IS known
in some places to run through the white
limestone to the white porphyry. Two
distinctly different classes of ore have
been found: carbonate of znz (malny
the mineral known as smithsonite) and
sllicate of zinc (the mineral called Gala
mine.) In some Instances these are
associated, but in others they are quite
distinct. In the following description
of the minerals. the characteristics men,
toned first are those possessed by the
varieties known to occur at Leadville.
| sMITHsoNITE.
| Composition Carbonate of zinc.
| = s
zinc
Lustre-Dull and earthly when mas
sive, as it is- cemmonly-f found. -Raain1
GUS or CLASSY when crystalline.
Color Brown, yellow, gray, or green
the brown and yellow colors are usually
due to iron. When pure or unstained
it is white.
Fracture -- Uneven when massive
When crystalline, it splits or cleaves
readily in several directions. This
yields smooth. polished surfaces that re
fleet the light brilliantly; these reflect
ing surfaces are usually minute.
Hardness The impure, massive va
riety may be soft enough to crumble in
the fingers, but is usually harder.
When pure and crystalline, it is but
slightly softer than knife-blade. All
graduations between these may be
found.
Acid test-If placed in a glass vial
containing strong hydrochloric (muriat-
c) acid, it will effervesce vigorously
That is, it will cause the acid to appear
to boil because of the rapid evolution of
gas. Limestone will act thus also, but
a small piece of limestone, if held in
pincers, dipped in the acid, and then
placed in the flame Of an alcohol lamp,
will tint the flame red. Smithsonite
will not do this.
| Occurrence-All of the material sent
to the School of Mines from Leadville
has been of the dull, earthly, white to
brown, rather soft, massive variety. 1t
might easily be confused with impure
oxides of iron when dark colored, and
with limestone or altered feldspatic
rocks when lighter. The acid and flame
test, however, should distinguish it
from these.
cALAMINE
Composition -Silicate of zinc. When
pure it contains 81 per cent sine.
Luster-Glassy
Color-Often brown or yellow and
then opaque. Colorless or white when
pure. May then be transparent. Rare
ly greenish or blush.
Fracture-Splits or cleaves readily
in two directions and then yields long,
slender, smooth polished surfaces that
reflect light brilliantly
Hardness-May be scratched with a
knife but only powder will scrape off
when attempts are made to cut
it.
Acid Test-Will not effervssce or
dissolve in strong, cold hydrochloric
acid.
Occurrence-Usually found as coating
or stalactitic masses of more or less
transparent material with coarsely
radiating or divergent structure.
Sometimes one layer will be white and
rather transparent while the next will