the Corundum Stone, and its Varieties, &c. 325 
a fine sapphire blue colour. The hardness of this substance 
was such as to be equalled only by that of the sapphire itself ; 
and, in some of the pieces, instead of adhering to the outside, 
it was dispersed, in very small particles, within the interior 
part. 
As I cannot, even at this time, consider this blue substance 
as any thing else than the blue perfect corundum known by the 
name of sapphire, I still retain the opinion I formerly thought it 
right to adopt, namely, that the substance to which it adhered, 
and which I found in the province of Forez, was really a kind of 
corundum. I still think also, that the variety I observed in the 
degree of hardness, and in the specific gravity, of different pieces, 
was owing to their being mixed, in various proportions, with 
felspar. If it should happen that, among the remains of a col- 
lection of which nothing is left to me but a painful remembrance, 
(although, as I have before said, my present situation is such as 
much alleviates my regret,) any of the specimens above spoken 
of still exist, and should fall into the hands of well informed 
naturalists, I hope they will let them serve as a basis for fresh 
observations. The description of the Abbe Hauy is alone suf- 
ficient to show, that the above substance cannot possibly be a 
kind of felspar. I am sorry, however, that he did not join to his 
description, the analysis of the substance; it certainly would 
have been very interesting, particularly if, as would most pro- 
bably have been the case, the hardest pieces had been selected 
for that purpose. 
The great difference sometimes observed in different speci- 
mens of the same substance, is exhibited in a very striking 
manner, in the emeralds which I found, at the same period, in 
a large vein of the fore-mentioned rock, but which was situated 
MDCCCII. U u 
