The Washington times., 1915-03-12
MANY WHETSTONES
SHOWN IN EXHIBIT
Their Growth and Evolution With
Developments Of Man Illus
trated at Old Museum.

Tho growth and evolution of whet-
stones with the developments OF the
arts of man, is illustrated in an ex-
hibit in the division of mineral tech
nology in the old National Museum
building.
There is a special form of milestone
for nearly every purpose and these are
all shown in the exhibit that embraces
proper Sharpening stones or abrastSes
for Uses in various professions ana
trades and in household work, In their
finished state with photographs show
ing the methods of mining and manu-
facture.
Probably the first stone used for.
abrasive purposes was sandstone,
very widely distributed rock, and 1t IS
still used today It's coarse grit and
even grain first attracted attention,
while the rough edge that 1t gave was
all that was then required. with the
progress of the arts there began q
search for various stones which could
be used for sharpening objects OF dif-
ferent sorts, so that today. nor only
sanestones. but mica schists' states,
and emery stones are used, besides
several artificial compounds.
Found In Arkansas.
The hard, white, compact sandstones
found near Hot Springs. Ark, are
among the best 'whetstones known,
equaling, If not surprising, the Tur-
key stone which for years has been
considered one of the best. This
Arkansas stone is known as Novacu-
lite, and occurs in two or. three
grades, intended for use with certain
tools. The hard, f1int-like stone should
be used only to sharpen instruments
made of the very best steel. requiring
very keen edges and points. such as
those used by surgeons, dentists, ana
jewelers.. The other grades. although
composed of the same ingredients, arc
more porous the sand grains ere not
as close together, and rougher edge
is given to the sharpened tool be-
cause Of their more porous nature
these stones cut faster. proving suit
able for the finer edged tools OF car
penters, machinists, and engraVers
and for honing razors.
Indiana and Ohio supply Whet'
stone made from a sandstone or 9
coarser grain than the NoVacullte o'
Arkansas, but nevertheless quite uni.
form. 1t may be used with elther OF
or water, and is useful Tor sharpeninN
nary carpenters tools. But since 1t Il
easily cut and groved by hard anc
sharp steel. the fine instruments ol
dentists and surgeons should not bt
edged or pointed on tnlS Stole'
Composed of Mica.
Scythestones and moving machine
stones are practically all made from
mica schist rocks found in New
Hampshire and Vermont. These rock
are generally of n dark gray color
and composed of very thin sheets o
mica and quartz crystals intcrlam!
mated. The grit of the schist is not
sharp as that of the sandstone. pc
cause 1T cont"ins foreign materla
other than SILICA which prevents tn
quartz grains from abrading Freely;
Mica schist stones wear down quickl.
from constant use-an advantage rathe
than a disadvantage, for us they wea
down, more of the hard silica grain
are exposed to do the sharpening
Neither Oil nor water is needed to keel
the pores of the stone open, as witt
other whetstone rocks. Scythes requir
stones with these qualities, and conse
uuently much schist rock is made int
scythe estones. Some of the fine graine
schists which produce we'll FINISHED
edges are made into carpenters benC
stones.
A simple experiment made about ff
teen years ago led to the discovery o
Carborundum and crystolon. BY heat
ing a mixture of salt, sand, saWduSt
and powdered coke In an electric fur
Carborundum and crystolon were pre-
duced.
These crystals are extremely hare
cutting glass easily, and. in fact, a
most any substance except the diamonC
are intensely sharp. and infusible g
any known heat-properties peculfarl
adaptable for grinding prposes and fc
refractory materials. The carborundui
and crystolon crystals are removed frol
the electric furnace after thirty-si,
hour run, washed with a dilute ac'
solution, ground, and sized. Eight {
ten diffirent sizes of grains are obtaine'
and a corresponding number of grade
of wheels and stones are made fro
them.
Mixed Into Paste.
The graded grains of these substanc
are mixed into a paste with IA bond
porcelain, water glass. or rubber, al
nodded into many varied forms
stones and wheels. After air dryin
the raw wncels are put into kilns al
baked, and are then ready for us
There are wheels for all kinds of wor
varying from three feet in diameter f.
use in foundries, to one-quarter I'M
for dental work.
Besides the wheels. these hard, sha
crystals are made into razor and kni
homes, paste for valve grinding, al
glued to cloth to be used like sand al
emery paper. The crystal grains =
used by gem and stone cutters, and f
saving building stones.
Emery cloth and paper are very We
known commodities, but are little us
today because the artificial abrasiv
are Just as effective and cheaper. l.
permcnts to obtain an artificial produ
having the main characteristics
emery resulted in the making of alu
dom and aloXite, both of which 4
shown in the museum series.