Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1913-05-17
MICA IMPORTANT MINERAL.
United States Has Large and Valuable
Dsposits-Imports Exceed Domestic
Production in Value.

Tho mineral mica has become an i'm
portant article in the industrial world,
and large manufacturing companies,
chiefly manufacturers Of electrical ap-
paratus and machinery, wall papers, and
stoves. are dependent on a regular sup.
ply of it. Properties which render mica
valuable in these trades are its perfect
cleavage into tough, flexible, and elastic
sheets, transparency, nonconduetivity oi
electricity, and the brilliance of the
small scales of ground material. Mica
is sometimes called isinglass when used
in stoves and lamp chimneys but should
not be confused with the original isin.
glass, gelatiuous material obtained
from certain fish. The mica of COM
msrce includes two principal varieties,
muscovits and phlogopite, but small
quantities of biotite have been used.
Muscovite is known as clear or white
mica, phlogopite as amber mica, and
biotite as black mica.
Mica is mineral of widespread occur
renee in the rocks of the earth's crust,
according to Douglas B. Sterrett, of the
United States Geological Survey. The
mica suitable for industrial uses is found
in coarse-grained rocks. Deposits OF
commercial or possible commercial value
are known in many countries, but the
principal sources of supply at present
are India, United States and Canada.
In the United States muscovite is the
only variety mined, but small quantities
of biotite have been obtained as a by
product.
MICA USED FOR DECORATION.
Large quantities of scrap mica-small
sheets and the waste from the manufac-
ture of sheet mica-are ground for diff
ferent uses, among which are the decor.
alton of wall paper, and the manufacture
of lubricants, fancy paints and nodded
mica for electrical insulation. Groun
mica applied to wall paper gives sill
very luster. When mixed with gre ase
or oils finely ground mica forms an ex-
cellent lubricant for axles and other
bearings. Mixed with shsllac or special
compositions, ground mica is nodded in
to desired forms and is used in insula-
tors for trolley wires. Ground mica for
electrical insulation must be free from
metallic minerals. Mica used for lubri.
cation should be free from gritty matter.
For wall paper and brocade paints a
ground mica with high luster ia requir-
ed, and such luster is best obtained by
using clean, lightrcolored mica and
grinding it under water. Coarsely
ground or "bran" mica is used in in
creasing quantities to coat the surface of
composition roofing material to prevent
the tar or other Ingredients used in it's
manufacture from sticking when the
sheets are rolled for shipping.
EIGHT STATES PRODUCE MICA.
The total value of mica produced in
the United States in 1912, according to
Mr.. Stsrrett, was 1881 1896, a decrease of
$23, ,00S compared with 1911. The pro-
duction came from eight States-North
Carolina, New Hampshire, Idaho, New
Mexico, South Carolina, Colorado, South
Dakota and New York, named in the
order of the value of their output. The
production Of sheet mica amounted to
845, 4S3 pounds, valued at $2S2, 1928, COM
pared with ], 1887, POI pounds, valued at
$3l0, ,254, in 1911. The total output of
rough-trim sheet mica amounted to
over 1000, 900 pounds in 1912.
The mica mines of the United States
are capable of large annual production
and could be made to supply all but the
small part of the demand which calls
for the softer Canadian amber mica.
This could be accomplished if some of
the largest already proved mines in
North Carolina, New Hampshire, South
Dakota, Idaho, New Mexico, Virginia,
and Colorado were operated on large
scale or even as they have been worked
in the past. Other deposits in these
and many other States could be develop
ed to meet increasing future demands.