Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1909-07-10
MICA MINING.
South Dakota is Second State in the Pro.
duction Of Mica.

South Dakota is Second State in the Pro
duction Of Mica.
In pamphlet just published by th'
United States Geological Survey, Doug
las B. Sterrett says of the South Dakot,
mica mining industry!
The mica mines described in thi'
paper are all located within radius o
eight miles of Custer, S. D., in the south
ern part of the Black Hills. This ares
includes the better deposits of mica &c
far located, though some deposits occur
II to Is miles north of Custer, on the
north side of Harney Peak, With the
limited time available for examination il
was not possible to visit all the mines
even of those around Custer. The field
notes for the present article we're OBJ
tanned during the first part of August
1908. At the time of visit there were
but two mines in operation--the No.
or New York mine, and the No. 2 OF
White Spar mine, both of the Westing'
house Electric and Manufacturing COM
pany.
Previous to 1906 the production oi
mica in South Dakota had been small for
several years, being often only that OBJ
tained from assessment work on the
claims, but in that year the Westing-
house company took up several mines
and prepared for systematic and exten.
sive work. The success oftbis company
has raised South Dakota to second rank
among the mica producing states. Of
the l,060.l82 pounds of sheet and 3,025
tons of scrap mica, with total of 1892,
Ill, produced during 1907 in the United
States, South Dakota contributed nearly
third. If some of the mines now idle
or worked in a desultory way could be
equipped for operation on large scale,
the production of South Dakota would be
largely increased. Ifthe total production
of mica in the United States could be in
creased nearly three times, the domestic
production with the exception of the
soft amber" or phlogopite mica necess-
ary in the manufacture of commutators
for electric dynamos and motors, aquan-
tity of this variety would still have to be
imported from Canada, as there are no
deposits known to be Of value in the
United States. It is probable that other
consumers of mica could develop deposits
in one or more of the mica regions of the
United States and supply their own de-
mands as the Westinghouse has done
that is, with the exception of the soft
"amber" mica.
The commercial applications of mica
are numerous. The principal use of the
present day is in the manufacture of
electric apparatus. In the early days of
the industry in this country the chief de-
mand for mica was for glazing purposes,
principally in stove manufacture. This
has now become one of the lesser uses,
along with the manufacture of gas lamp
chimneys, etc. The value of good sheet
mica suitable for glazing is higher than
that of the material suitable for electric
purposes. The demand for glazing mica
is insufficient to use all the sheet mica,
produced, 80 only the best quality and
larger sheets are used for this purpose.
"Micanite" or built-up mica board, for
the manufacture of which smaller sheets
can be used, is an amply good substitute
for large sheet mica in electric work.
Mica from one locality may have
properties rendering it more suitable for
certain applications than that from an
other, though not necessarily excluding
it from other uses. Thus, the Canadian
"amber" is especially adapted to COM
mutator insulation; the best North Caro-
lima rum" colored, when in thick sheets,
or "white" mica, when in thin sheets, is
we'll suited for glazing. The South Dako-
Ia mica in general is little softer and
less clesr than the North Carolina mica
and therefore not so satisfactory for
glazing. 1t is, however, we'll adapted to
the manufacture of "micanite" and other
products for use in electric machinery
and apparatus.