Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1911-07-08
Douglas B. sterrett, in Mining Science

as the copper of the commutator seq
ments, therefore wears down evenly
without causing the machine to spark.
A large quantity of the sheet mica used
in electrical apparatus is built into "mi-
canite" or "mica board, the thin sheets
being built up layer after layer with
shellac, with or without tissue paper,
and then subjected to great pressure
under heat to dry out the shellac.
Sheet mica with black specks of mag
netic iron between the lamine is inferior
to clear mica for electrical insulation.
Such mica is used however, in electrical
apparatus conveying only currents of
fairly low voltage. This variety of mica
is satisfactory if used with discretion,
but some electrical manufacturers will
not use it in any of their apparatus.
A large quantity of scrap mica; that
is, mica too small to be cut into sheets
and the waste from the manufacture of
sheet mica, is ground and used in many
ways. Among these are the manufacture
of wall papers, lubricants and fancy
paints, and of nodded mica for electrical
insulation. Ground mica applied to wall
paper gives them a silver Iuster. When
mixed with grease or oils finely ground
mica forms an excellent lubricant for
axles and other bearings. Mixed with
shellac or special compositions, ground
mica is nodded into desired forms and
is used in trolley wire and other insula-
tors. Ground mica for electrical insula-
tion must he free from gritty matter.
For wall papers and brocade paints
ground mica with high luster is re-
quired, and such luster is best obtained
by using clean, light-colored mica and
grinding it under water. Coarsely
ground or bran" mica is used to coat
the surface of composition roofing mate
rial to prevent the tar or other compost
tion used in its manufacture from stick
ing when the material is rolled for ship.
ping.
The total value of the mica produced
in the United States in 1910 amounted
to $685., ,097. The product came from
seven States: North Carolina, South
Dakota, New Hampshire, Colorado,
South Carolina, New Mexico and Massa-
chusetts, named in the order of the
value of their output. South Carolina
and new Mexico returned to the list of
mica a-producing States in 1910, no pro-
duction having been reported from these
States in 1909. A small output was re.
ported from Massachusetts, which had
reported no production for several years.
Virginia, Alabama, New York, Georgia
and Maine failed to report an output of
mica in 1910, though each reported
production in 1909. The value of the
production of mica in 1910
was greater by $685. than in 1909,
and was greater than in any other year
except 1907, when it amounted to
$392,ll1.
The production of sheet mica amount
ed to 2,476, 100 pounds, valued at $685.
S32, an increase of 666,6OS pounds in
quantity and of $49, $50 in value as COM
pared with the output of 1909. The pro-
duction of sheet mica reported from the
different States each year is quite varia-
BILE and it is difficult to make distinc-
ton between the small sheet mica for
punched forms and scrap mica. The
variation is also due in part to the fact
that in some years some of the producers
complete the manufacture of more of
their mica than in other years, thus re-
porting smaller quantities of sheet mica
and larger quantities of scrap mica than
in years when less of the mica is trim
med into sheets. In 1910 the largest
production of sheet mica was reported
from South Dakota, but in 1909 the larg-
est production was reported from North
Carolina.
The production of scrap mica amount
ed to 4,065 tons, valued at $53, ,265, a
decrease of 25 tons in quantity and an
increase of $7,2lS in value as compared
with the figures for 1909. The increased
value was due to an improvement in
the price of scrap mica in North Caro-
lima, which furnished nearly three.
fourths of the total production.
The value of the production of mica
in North Carolina in 1910 was $3.50, 46O,
as compared with $l4s, 424 in 1909, an
increase of $s2,O46. The productio n
reported in 1910 consisted of 455,02O
pounds of sheet mica, valued at $l93, 223
and 3,O74 short tons of scrap mica val
ued at $37, ,237. The production in 1908
consisted of 1,296,27 pounds of sheet
mica valued at $l22,246, and 2,eO7 short
tons of scrap mica valued at $26,l7S. II
is evident that large quantity was re-
ported as sheet in 1909, and, further,
that the production for 1910 included a