*2$6 Count de Bournon's Description of 
attention as I have since done, not only to corundum, but 
also to every thing relating to the substances which accom- 
pany it. 
The most usual colour of this substance, as I have already 
said, is gray, slightly inclining to green, which is sometimes 
mixed with a small portion of brown. It possesses a pretty con- 
siderable degree of semi-transparency, which may be compared 
to that of calcedony, or more properly to that of the stone known 
by the name of cat's eye. Its hardness is inferior to that of 
quartz ; but appears to be exactly the same as that of felspar. It 
gives sparks, when struck by steel ; and, by collision, emits a 
yellowish phosphorescent light. Friction does not cause it to 
give any signs of electricity. 
This stone may be divided with great facility, in the direction 
of two opposite and parallel faces ; and the fractures thereby 
obtained have a brilliant lustre, exactly resembling that of the 
fractures of corundum. Upon these fractures may be observed 
very fine but very evident striae, which indicate that the laminae 
have a direction different from the above ; but I have not yet 
been able to obtain an even fracture, in the direction of these 
striae. All fractures made in any other direction than that first 
mentioned, are irregular and unequal; very often also they are 
dull, and somewhat similar to that of wax. 
The mean specific gravity of tiiis substance, taken from four 
trials, which differed very little from each other, is 2643. 
This substance is fusible by the blowpipe, like common 
felspar. 
The result of the analysis of this substance, made by Mr. 
Chenevix, is, in many respects, similar to that of the analysis 
