Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1893-09-30
MICA IS THE STUFF.
In These Days the World Gould Hardly
Worry Along Without 1t.

Mica nils the lnterstlces 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 multifarious uses to
which mica a be applied. Thus the
law Of necessity changes in its relation
to all things.
Mica is now as essential to the yari-
ous uses of electricity as this great
force is necessary to human progress.
In all appliances for electrical lighting
and power the most important recip-
rOcal agent entering into their mech
auism is mica. All armatures are
built up with its insulation, whether
for dynamos, motors, generators, or
transformers. Without its use as an
Insulation the core of the armuture
would burn out with a flash. But by
placing sheets of mica between the
thin sheets of iron, which are secured
to the shaft that runs through the
drum Of the armature, insulation be-
comes perfect. Thus armatures "
even the largest generators can be run
for t~wenty-fOur continuous hours with
out heating them more than 50 deg.
Fahrenheit above the temperature OF
the surrounding air. BY this use Of
mica the lines of force are dissipated,
but do not lose any Of their electrical
energy.
In all electrical safety appliances
mica also performs an important part
as an insuiator. To its infusible and
indestructible nature much of the
success of the rheostat can be ascribed.
This wonderful mechanism, which is
applied as q motor starter, q governor
of speed, a reversing switch, and an
automatic safety switch, is absolutely
%freproof, and can be subjected TO a
red heat without mechanical injury.
This is rendered possible by making
the resistance Of thin plates Of iron
packed closely together, but separated
by mica.
Iurs 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 Il thousand minor ones,
which make it the constant and will
ing servant Of the greatest pover that
man has turned to intelligent subjuga-
ton.
Mica is also an important factor in
many branches of manufacture and
art. Owing to its peculiar elasticity
and toughness, qualities in which it IS
not excelled by anything natural or
artificial, it is used as an absorbent OF
nitro-glycerine, and when SO used eX-
plosions by percussion are rendered
almost impossible, 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 feathery form.
The %Drismatic or foliated mics
also used by passing it through q mil
This vastly increases the mica's bulk
aud forms masses of bran-like scales,
translucent and beautiful, The French
silver holdings are also made with
this ground mica. The unalteraole
nature of mica and the fact that 1t en-
tirely ~resists the action of corrosive
smoke and dust, make It a val
liable material for edifcial decoration.
1t can be readily colOred or metallzeq,
an its transparency preserves IN an
Irs pristine beauty anything TO "hleh
j! is applied. This ground mica IS also
used as a lubricant and axle grease
ana for such purposes has no superior
except plumbago. Coarsely pui'eI--
lied it is also used for roofing material
and as a tireprooiing for iron safes
The cleavage Of mica is so perfect y
is estimated that it can be spit or az
yided into leaves $50, 900 to an men.
Much of its commercial value depends
upon this wonderful property OF laml-
nation. The largest plates OF me"
with such foliaciOus structure are on
tanned from the Siberian mines anu
they sometimes attain a diameter q
i've and seven feet. Crystals over
two feet in diameter have been fouuu
in Pennsylvania. eighteen to twenty
four inches in New Mexico, and TOUR
teen inches in North Carolina. Biochs
of crystals weighing over one hunoreo
pounds are frequently mined. l.s
North Carolina mines are supposed "
be very ancient.
Mica plates found 10 them "hen
first discovered were trimmed to par
~ticular shapes, aud it IS supposed ihtS
were used for windows. mirrors au4
ornaments. The number OF the hi.lss
and The magnitude Of lhese aae.sli
operations excite wonder. some "
the mines are tunuglled to q cons"
able length. and distinctly sho" mafhs
of chiseI-shaped tools. Mica lu 'lus
form exists all over the earth. but AVs
n quantities Of any Commercial, ya'as'