34- ADAMANTINE SPAR. 
mortars, or in steel mills ; and is afterwards separated, 
according to the several degrees of fineness that are re- 
quired, by washing it in water, and suffering the grosser 
particles to deposit themselves. By this operation the 
liner particles, which remain suspended in the water, 
and which are obtained by decanting the water off, and 
suffering it to stand for a considerable time, are sepa- 
rated. The particles first deposited are again ground, 
and again agitated in the water, to separate the finest. 
By these successive operations the emery is reduced to 
a powder so fine that, when rubbed between the fin- 
gers, it communicates no sensation whatever of gritti- 
ness. In general those particles only of the emery 
which remain suspended in the water, after it has stood 
about half an hour, are used to polish metals. 
59. ADAMANTINE SPAR, or IMPERFECT CO- 
RUNDUM, is a very hard and nearly opaque stone, which 
varies much in colour, but is chiefly grey, with a greenish) 
brown, or bluish tint. 
It is usually found in the form of six-sided prisms, but it 
sometimes occurs in shapeless masses, has a foliated texture, 
and is about four times as heavy as zcater. 
The name of adamantine spar was given, by the 
British lapidaries, to this substance from its hardness 
being nearly equal to that of the diamond. It was 
originally discovered among the granite rocks of China; 
but it has since been found, and in greater purity, in 
Bengal and Ceylon. 
In a powdered state this substance has long been 
used by the artists of India and China for the cutting 
and polishing of precious stones, and even of the dia- 
mond ; but, though it will in some degree operate upon 
that gem, it is not sufficiently hard to bring out the 
peculiar beauty of it in a degree at all comparable to 
that which is effected by the European lapidaries with 
diamond powder. The Chinese also use adamantine 
spar for polishing steel, and in the composition of the 
finer kinds of porcelain or earthenware. For the cutting 
