Mountain advocate. (Barbourville, Ky.) 1904-1935, 1915-05-28
ARKANSAS GIVES
BEST MILESTONE
Novaeulte Found Near Hot Springs
Equals Abrsslves Imported AL
from Turkey. -....,3t
INDIANA STONE MUCH coARssa
Mica Schist Rocks from New Hsmp
shire and Vermont Keep
Scythes Sharp.

Scytnes Snarp.
Washington, ID. C.-Not many people
realize that there is a special sort Of
milestone for nearly every purpose.
The proper sharpening stones or ab.
rasyos for use in various professions
and trades and In household work are
exhibited in the division of mineral
technology in the older building Of
the United States National Museum
az Washington, II. c. The exhibit
shows specimens OF the crude and
partially prepared stones and the fin.
ishcl products ready for use. as we'll
as series Of photographs which illus
trgtc the operations Of mining and pre-.
pairing them.
Probably the first stone used for
abrasive purposes was sandstone, q
very widely distributed rock, and il IL
s'i.l used today. Its coarse grit and
even grain first attracted attention,
While the rough edge that it gave was
al that was then required. With the
progress Of the arts there began a
search for various stones which could
be used for sharpening objects OF diff
fereut sorts, so that today not only
s9udstCrus. but mica schists. states
and emery stones are used, besides
several artificial compounds
The hard. white. compact sand
stones found near Hot Spri,gs. Ark.
are among the best whetStCres known
cluali0g. H. not surprising. the Tur-
key Stone which for years has been
considered ore Of the best. This
Arkansas stone is known as novaculite
and occurs In two or three grades. In
tended for use with certain tools The
Lard, flint like stone should be used
only 10 sharpen instruments made of
,le very best steel, requiring very
L5ea edges and points, sucn as those
used by surgeons, dentists aDi jewel.
Crs
The other grades, although compcs-
ej OF the same ingredients, are more
porous tie sand grains are not as
close together and a rougher edge is
given O. Che happened tool Because
az uEsir more porous nature these
stones cut faster, proving suitable for
the Gnor edged tools OF carpenters, ma.
,hiuists and engrayers and honing
Tazors
Indiana and Ohio supply a whet.
stone made from sandstone Of coars-
or grain than the povaculite of ar.
kansas, but nevertheless, quite uni.
form II may be used with either oil
CT water, and Is useful for sharpening
household cutlery, peuEniyes OF ordin.
Cry carpenters tools But since ii Is
easily cut and groovei by hard and
sharp steel, the hue Instruments OF
dentists and surgeons should not be
edged or pointed on this stone
Scythcstunes and moving machine
stones are virtually all made from
mica sghist rocks found in New Hamp-
shire and Vermont These rocks are
generally Of a dark gray color and
composed Of very thin sheets OF mica
and quarty crystals interlaminated
The grit of the schist Is not as sharp
as that OF the sandstone, because it
contains foreign material other than
SILICA, which prevents the quartz
grains from abrading freely Mica
schist stones wear down quickly from
than a DISADVANTAGE. Tor as they wear
down, more OF the hard SILICA grains
ere exposed to do the sharpening
Neither Oh nor water is needed 10 keep
the pores of the stone open as with
other milestone rocks. Scythes re-
uuire stones with these qualities. and
consequently much schist rock is
made into scytLestones Some OF the
fine grained schists which produce
well-Gnished edges are made into car.
penter's bench stones.
A simple experiment made about Is
years ago led 10 the discovery Of Car.
borundum and Srystolon; by heating
a mixture Of salt, sand, sawdust and
powdered coke I'm an electric furnace
the variegated Colored crystals OF Car !
borundum and Srystolon We're produc.
ed. These crystals are extremely hard, I
cutting glass easily, and, in fact. al
most any substance except the dia'
mond: are intensely sharp, and infus-
ible at any known heat-properties
peculiarly adaptable for grinding pur- /
poses, and for refractory materials. /
The Carborundum and Sarystolon erys. |
tails are removed from the electric
furnace after a 36hour run. washed .
with a dilute acid solution, ground and
sized
Eight or 10 different sizes Of grains
are made from them. The graded
grains Of these substances are mixed .
into a paste with bond OF porcelain,
water-glass, or rubber, and nodded in-
TO many varied forms OF stones and
wheels. After air drying, the raw
wheels ar put into kilns and baked,
and are then ready for use. There are
wheels for all kinds Of work. varying
from 3 feet in diameter for use In
foundries. TO one-quarter inch for den
tai work. Besides the wheels. these
hard sharp crystals are made into
razor and knife homes, paste for valve
grinding and glued IN cloth to be used
like sand and emery paper. The crys-