the Corundum Stone, and its Varieties , See. 301 
MATRIX OF IMPERFECT CORUNDUM FROM CHINA, AND SUB- 
STANCES WITH WHICH IT IS ACCOMPANIED. 
This matrix is totally different from that of the imperfect 
corundum of the Carnatic, being a granite rock, composed of an 
aggregated mixture of felspar, fibrolite, mica, and very attract- 
able black oxide of iron. I have not yet seen in it any particles 
of that particular substance, already described, which composes 
the principal part of the matrix of imperfect corundum from 
the Carnatic. 
The four substances above-mentioned, are unequally distri- 
buted throughout the mass ; some pieces being composed almost 
entirely of one of them ; while, in other pieces, those substances 
are mixed together in various proportions, and sometimes in 
nearly equal ones. The crystals of corundum are disseminated 
in the mass, in the same manner as those of the Carnatic are 
in their matrix ; but, as the particles of the matrix now treated 
of have a much stronger adherence to each other, and also to 
the crystals of corundum, it is difficult to detach the said crystals 
from the matrix, without breaking them. 
The felspar has, in this matrix, the same appearance it usually 
has in granites. Its colour is generally reddish; very often, 
however, it is of a grayish white colour. I have never observed 
it to have any. determined crystalline form ; but, when it is in 
masses of a certain size, their texture is evidently laminated. 
The mica has a silvery appearance, sometimes inclining a 
little to a yellowish colour, at other times to a greenish one. Its 
laminas are frequently united together, so as to form prisms, 
which are pretty thick, but most commonly of an irregular 
mdcccii, R r 
