5^ Count de Bournon’s Description of a 
OBSERVATIONS UPON THE DIFFERENT KINDS OF SULPHURET OF 
COPPER. 
The triple sulphuret of lead, antimony, and copper, described 
by me in the former part of this Paper, cannot fail to be con- 
sidered as a substance highly interesting both to mineralogists 
and chemists, as it serves to show the true nature of the triple 
combination which sulphur enters into, with lead, antimony, 
and copper. The difference existing in the form, the specific 
gravity, the hardness, and all the other external characters of 
this triple sulphuret, when compared with those of the gray 
tetraedral sulphuret of copper, seems to me to demonstrate, that 
the antimony and the lead which have been so frequently sup- 
posed to be constituent parts of the last-mentioned ore, are 
nothing more than accidental mixtures ; and that, when they 
happen to be met with in that ore, they have been introduced 
merely by the heterogeneous attraction of aggregation, and are 
foreign to its substance. The same opinion may, I think, be 
fairly adopted, respecting the silver which is sometimes found 
in it. If these metals were really contituent principles, how 
can we suppose, that the presence or the absence of one or 
more of them, and the great difference that exists in their 
proportions, (as is shown by the various analyses which have 
been made,) should occasion no variation whatever in the form 
of the sulphuret. Such a circumstance would be in direct oppo- 
sition to every observation that has hitherto been made on the 
subject. 
Having been, for a long time past, impressed with an idea, 
that iron and copper are the only metals combined with the sul- 
phur, in the natural composition of the gray tetraedral sulphuret 
