32 Count de Bournon's Description of a 
Its specific gravity is 57 65 ; * it is consequently superior to 
that of sulphuret of copper, or sulphuret of antimony, but very 
inferior to that of sulphuret of lead. 
The fractures of its crystals are not smooth, neither are they 
lamellated in any particular direction, but are generally granu- 
lated, and have rather a coarse grain. 
The crystals of this substance are very brilliant, and often of 
a very large size. I have seen some that were more than an 
inch in length, and of a proportional height : but, as most of 
them have a great number of facets, and are frequently very 
irregularly shaped, on account of the inequality of their increase, 
it becomes very difficult to determine their form ; particularly as 
the crystals most commonly found, are those which differ most 
from the primitive form, to which, on that account, it becomes 
very difficult to refer them. For this reason, I have resolved to 
give a particular description of every thing that relates to the 
crystalline forms of the substance; hoping that I shall, by that 
means, contribute to promote the knowledge of a character so 
important in the study of mineralogy. 
Primitive Crystal. The form of the primitive crystal is a rect- 
angular tetraedral prism, which has its terminal faces perpen- 
dicular to its axis, as in Plate II. Fig. 1 ; but I have never yet 
observed, in all the specimens I have seen of this substance, the 
above-mentioned prism entirely destitute of secondary facets. 
* Of two trials of the specific gravity of this substance, taken at six months 
distance from each other, the first gave me 5765, the second 5763. It is evident that 
it is scarcely possible to approach more nearly to that found by Mr. Hatchett, 
namely, 5766 ; and this constancy in the above character, may be considered as a proof 
of the state of purity habitual to this sulphuret. 
