triple Sulphuret, of Lead , Antimony , and Copper , &c. 45 
for instance, granulated quartz, both of a fine and of a coarse 
grain, quartz in stalactites, &c. we are acquainted with several 
kinds of true concrete quartz, whichforms veins in primitive rocks, 
in the same manner as carbonate of lime forms veins in secondary 
rocks. All these substances have the appearance peculiar to 
quartz, and show nothing that is at all analogous to that appear- 
ance which so strongly characterises calcedony; the latter, also, 
possesses a degree of hardness superior to that of any of the 
others. Besides, quartz in a concrete state is often found acci- 
dentally mixed with martial argill ; a circumstance that, as is well 
known, frequently happens to calcedony. In the former case, a true 
jasper is formed, which has a quartzose base, instead of having, 
as in the latter case, a base of calcedony. The appearance of 
these two kinds of jasper is so different, that the most inex- 
perienced eye cannot fail to distinguish them at first sight. 
Many other facts might be added, in support of what I have 
said. Calcedony, for example, is easily decomposed : there are 
few masses of this substance of any considerable size, few frag- 
ments of flint, jasper, &c. which have lain for any length of 
time upon the surface of the earth, that do not afford a demon- 
stration of it. Most kinds of cacholong are nothing more than 
the effect of this decomposition, in a more or less advanced 
state, which (as happens in the girasol, but in a less perfect and 
less striking manner) causes the stones in which it takes place, 
to possess the property of becoming transparent in water. 
Quartz, whether in the most perfectly crystallized state, or in 
that in which its crystallization has been the most disturbed, 
possesses nothing which can be compared with the above pro- 
perty. I cannot therefore consider quartz as calcedony, properly 
so called ; nor can I consider the substance I have distinguished 
