284 Count de Bournon’s Description of 
texture, in which the grains are often pretty large, so as to be 
easily distinguishable by the naked eye. When these pieces are 
in a perfect state, the grains have exactly the same colour, and 
the same degree of semi-transparency, as those of the preceding 
more compact kind. If examined with a lens, the laminated tex- 
ture of these grains is very evident ; and there seems to be, at 
the first view, a very distinct crystal in each of them. But, if 
we endeavour to determine the form of any one of these crystals, 
we find that it is absolutely impossible to do so; as the greatest 
part of the small facets we perceive, are nothing more than 
facets formed by compression. I thought, indeed, that I could 
distinguish some traces that indicated an obtuse rhomboid ; but 
not in such a manner as to permit me to state the fact with 
certainty. These grains have but a weak degree of adherence to 
each other ; in consequence of which, the stone may often be 
broken by a very slight effort. 
It is, however, still more common to meet with this substance 
in a state wherein it has undergone, at the surface of each of 
the grains of which it is composed, an incipient decomposition, 
that gives them a whiter colour, thereby obscuring, and indeed 
often destroying, that semi-transparency which I mentioned 
as being a character of this substance, in its two preceding 
states. When this is the case, if some pieces of the stone are 
put into nitric acid, an effervescence soon takes place, the 
strength of which is in proportion to the degree of decomposition 
the stone has undergone ; but this effervescence, in a short 
time, entirely ceases. It seems, from this circumstance, that the 
lime contained in the stone, (which, as will be hereafter seen in 
the account of its analysis, Mr. Chenevix found to amount to 
15 parts in 100,) being exposed to the action of the air, by the 
