Mr, Greville on the 
410 
proceed to give an account of the varieties of Corundum stone, 
which I have obtained from India and China. 
In the year 1786', Col. Cathcart sent me a small fragment 
of a stratified mass from Bengal, with this label ; “ Corundum, 
“ much inferior in price to that of the Coast." It is of a purplish 
hue; its fracture like compact sand-stone; and a confused 
crystallization appears in all parts of the stone, by fibres of a 
whiter colour, from which the light is reflected, as in feld- 
spar, &c. 
I have since obtained a larger lump of the stone, of the same 
texture, but rather paler in its purplish hue. Sir John Mac- 
Gregor Murray informed me that it is called by the natives 
of Bengal, Corone, and used for polishing stones, and for all 
the purposes of emery. 
Its specific gravity is 3,87b. 
Capt. Colin Macauley procured a lump of Corundum from 
a sikuldar , (a polisher, this term is most appropriate to polishers 
of steel, ) in whose family it had been above twenty years em- 
ployed, for grinding and polishing stones or gems. The use 
to which it had been so long devoted had occasioned grooves 
in its surfaces, which facilitated greatly the examination of its 
structure. It is about inches long, inches broad, and 
above two inches thick. On one of its broad surfaces are two 
oval grooves; one of them is four inches long, one broad, and 
of an inch deep. On the opposite side is a shorter oval groove, 
above 2-f- inches long, 1 inch broad, and one inch deep. In 
these grooves, the ends of the laminae of the mass reflect 
the light, like the crystals. It serves as a specimen of the 
simple apparatus of an Indian lapidary. Stones polished in 
these grooves would be of the common India polish and form, 
