Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1893-08-26
Mica.

y Under the above heading the Chicag,
Inter Ocean publishes an article which
viii! give the reader fair idea Of tn,
innumerable uses to which mica is nov
i put, and which also explains why it i
that mica mines which were practicall,
1 vaiuele few years ago can now b,
worked with profit TO their owners. II
will be Of special interest TO those who
are interested, directly or indirectly, il
! the mica industry Of the Southern Hills
which has recently received such
gratifying impetus
Mica fills the interstices Of modern
progress. A few decades ago we were
seeking practical use and market for the
output OF mica mines already found
now we are seeking new mines to supply
the muliifarious uses to which mica car
be applied. Thus the law of necessity
/ chanoes IN va y-i-.ias "a, all .thinss.-
Mica 10 now essential TO the variou,
uses OF electricity as this great force il
necesssrr to human progress. In all
| appliances for electrical lighting and
power the most important reciprocal
agent entering into their mechanism is
mica. All arrnature are built up with
It's insulation, whether for dynamos
motors, generators, or transformers
Without its use as an insulation the core
OF the armature would burn ont with a
fash. But by placing sheets Of mica be-
tween the thin sheets Of iron, which are
secured TO the shaft that runs through
the drum of the armsture, insulation
becomes perfect. Thus armatures of
even the largest generators can be run
for twenty four continuous hours with
out heating them more than s00 Fahren-
heit above the temperature Of the sur
rounding air. BY this use Of mica the
lines OF force are dissipated, but DO not
lose any Of their electrical energy.
\ In ali electrical safety appliances mica
also performs an important part as an
insuator To its infusibe and inde-
structible nature much Of the success Of
the rheostat can be ascribed. This
wonderful mechanism, which is applied
as motor starter, a governor of speed
a reversing switch, and an automatic
safety switch, is absolutely fireproof.
and can be subjected to a red heat with
out mechanical injury. This is render
ed possible by making the resistance of
thin plates Of iron packed closely to-
gether, but separated by mica.
Thus the lines Of force operate on the
same principle as in the armature
Aside from these important uses of mica
in electrical apparatus. it is also applied
to thousand minor ones, which make
il the constant and willing servant Of
the greatest power that man has turned
to intelligent subjugation.
Mica is also an important factor in
many branches OF manufacture and art.
Owing to its peculiar elasticity and
toughness, qualities in which il is not
excelled by anything natural or arti-
fetal, it is used as an absorbent of nitro
glycerine, and when so used explosions
by percussion are rendered almost i'm
possible, while at the same time nothing
is taken from the energy of the nitro
glycerine when exploded by Eliminates
or similar device. For such purpose
the plumose mica is used, or that in
which the scales are arranged in feath-
Ths prismafic or foliatsd mica il also
used By passing il through mill. This
vastly increases the mica's bulk and
forms masses Of b an like scales, trans
lucent and beautiful. The French silver
mouldings are also made with this
ground mica. The unalterable nature
of mica and the fact that ii entirely re-
sists the action Of corrosive acids, smoke,
and dust, make it a valuable material
for edifcial decoration. 1t can readily
be colored or metaized. and its trans
parency preserves in all its pristine
bes uty anything 10 which j. is applied.
This ground mica is also used as a lubri-
cant and axe grease, and for such pur-
poses has no superior except plumbago.
Coarsely pulverized, il is also used for
roofing material and as a fireproofing
for iron safes.
The cleavage of mica is so perfect il is
estmated that it can be split or divided
into leaves 250 900 10 an inch. Much oil
its commercial value depends upon this
wonderful property of lamination. The
largest plates of mica with such foliaci-
ons structure are obtained from the
Siberian mines, and they sometimes at
| tain diameter of five and seven feet
CRYSTALS oyer two feet in diameter have
been found in Pennsylvania, eighteen
Ito twenty -four inches in New Mexico
and fourteen inches in North Carolina
/ BLOCKS Oh ONNi cAs
hundred pounds are frequently mined
| The North Carolina mines are supposed
| TO be very ancient.
Mica plates found in them when first
discovered were trimmed to particular
shapes, and it is supposed they were
used for windows. mirrors, and orna
ments. The number Of the mines anc
the magnitude Of these ancient opera
tons excite wonder. Some of the mines
are tunneled TO a considerable length
and distinctly show marks of chisel
shaped tools. Mica in some form exists
all over the earth, but not in quantitie
of any commercial value. 1t can h
found in granite and quartz rubellite
green tourmaline, feldspar, lepidolit
aud other minerals, also in granula
limestone, gneiss. and slate. II varies
in color from white through green, yel
lowing. and brownish shades to black
| Its chemical composition is silicite o
alnmina and potash, with small amoun
OF iron, msgnesia and soda, and abou
sfys per cent water.
II Se----