326 Count de Bournon's Observations on a new 
be supposed very brittle, yet they resisted my efforts to break 
them, in a very remarkable manner. 
The resistance above spoken of appearing to me analogous 
to that of hard stones, I resolved to examine, with the most 
scrupulous attention, every thing relating to the peculiar cha- 
racters of this substance. 
Its hardness is very superior to that of common carbonate of 
lime, being such as to scratch very easily the fluate of lime; 
and, when rubbed with force upon glass, it takes off the polish 
of its surface, and sometimes leaves scratches upon it. 
Its specific gravity, I found to be 2912. 
This substance, of which I have since had an opportunity of 
observing a great number of specimens, I have always found to 
be without colour; and its crystals are very often perfectly 
transparent. 
When powdered, and thrown upon a piece of iron heated 
nearly to redness, in a place that is perfectly dark, it occasions 
a very weak phosphorescent white light ; this light is only suffi- 
cient to mark the place where the powder is thrown. 
Its lustre is much greater than that of common carbonate of 
lime. 
When put into nitric acid, a violent effervescence is produced; 
and it is very quickly dissolved, without leaving the smallest 
residuum. 
Although this substance strongly resists any effort made to 
divide it by splitting, yet it shows a tendency to admit of being 
divided more easily in two directions, which would produce a 
rhomboidal tetraedral prism. I succeeded indeed, at last, though 
with great difficulty, and after many fruitless attempts, in pro- 
curing from it a perfect rhomboidal tetraedral prism, the angles 
