2^6 Count de Bournon's Description of 
possessed a degree of transparency very little inferior to that of 
the perfect corundum of Ceylon. The terminal faces of the 
crystals from the two last mentioned places, are very frequently 
what is called chatoyant ; a property of which I shall hereafter 
speak more particularly. 
The perfect corundum of Ceylon, whatever may be its colour, 
always has a greater or less degree of semi-transparency ; and 
very often is perfectly transparent. Sometimes, indeed, the 
crossed fissures already spoken of, as existing in the imperfect 
corundum, are also to be observed in the interior part of this ; 
but, when that is the case, they are less strong, and less nu- 
merous. The crystals of the perfect corundum have a smooth 
and brilliant surface ; and they show all the transparency their 
substance possesses, without its being necessary, as in the im- 
perfect corundum,’ to break them for that purpose. In general, 
when they have an inferior degree of transparency, whatever 
their colour may be, their terminal surfaces possess the appear- 
ance called chatoyant , which, as I have already said, is very 
frequently observed in the corundum of China, and in that of 
the coast of Malabar. 
In general, although the perfect corundum of a blue colour, 
or sapphire, has exactly the same characters as that which 
is of a different colour, it appears to me certain, if I may judge 
from the great number of specimens I have seen, that it more 
commonly possesses a perfect transparency, than that which 
is of any other colour. I have already made a similar obser- 
vation, in speaking of the imperfect corundum of the Carnatic. 
To this circumstance must be attributed, the superior value of 
an oriental ruby, if without defect and of a certain size, when 
compared with that of a sapphire of equal size and equally 
