54 Count de Bournon's Description of a 
nothing but copper, iron, and sulphur, in the following pro- 
portions ; namely, °f copper, of iron, °f sulphur. 
Perhaps we may, with some reason, consider the latter analysis, 
as that of this sulphuret in its purest state, and consequently 
as that which most decidedly declares the true nature of the 
tetraedral gray martial sulphuret of copper, when free from 
those extraneous metals that so frequently unite with it, by in- 
troducing themselves within its substance. 
This gray copper ore (the Fablerz of the Germans) is there- 
fore, in my opinion, shown to be nothing more than a simple 
combination of sulphur with copper and iron, in other words, a 
double sulphuret, of copper and iron ; but it is very apt, during 
its formation, to admit other metallic substances into its compo- 
sition, by the heterogeneous attraction of aggregation. When 
this double sulphuret is scratched with a knife, the powder ob- 
tained is sometimes of a black colour : this is always the case 
when the sulphuret is un mixed. At other times, the powder is of 
a reddish-brown colour ; and it may then be presumed, that the 
sulphuret contains a mixture of silver and antimony, generally 
combined together, in the state of red silver. 
I have seen many specimens of this substance, in which, by 
means of a lens, particles of red silver might be perceived. In 
some specimens, they might be seen with the naked eye. When 
this sulphuret is taken from a mine that contains sulphuret of 
lead, it very frequently contains some particles of the latter 
metal. 
On the other hand, however, I cannot consider, as most mi- 
neralogists do at present, yellow copper ore (the Kupferkies of 
the Germans) as a mere martial pyrites, or sulphuret of iron, 
holding copper interp osed within its substance. This ore also 
