6 o Count de Bourngn's Description of a 
phurets; among these forms, however, the octaedron (the 
only form mentioned by Mr. Werner) appears to me not to 
exist. To this species belongs that which, in Mr. Klaproth's 
analysis, afforded him of copper, XX_ Of iron, and of 
sulphur; and which Mr. Werner makes his second sub-species 
of vitreous copper, under the denomination of lamellated vitreous 
copper; but it is in fact a variety of the Buntkupfererz, not of 
the vitreous copper. It is true indeed, that this latter sometimes 
contains a portion of iron, but always a very inconsiderable 
one, within its substance; and, when that happens, the iron 
is totally foreign to its composition. Among the analyses of 
the various combinations of copper with sulphur, which Mr. 
Chenevix was so good as to make at my request, (the speci- 
mens for that purpose having been furnished by me,) one was 
that of a very pure sulphuret of copper, which came from 
Cornwall, and was in crystals of a perfectly determinate form. 
The constituent parts of this sulphuret appeared, by the analysis, 
to be XXL. of copper, and X^L of sulphur. In six others of the 
above-mentioned specimens, there seemed to be a mixture of 
iron, varying in proportion, from yX- to -X^.. Lastly, from the 
analysis of several specimens of the sulphuret last described, 
( Buntkupfererz,) which were of the colour of nickel, I am induced 
to believe that the proportions of the real constituent parts of 
this species, must be very nearly as follows, viz. from to 
XL of copper, and from XX- to XX- of iron, the remainder being 
sulphur. 
From what I have here observed, which however is to be 
considered merely as a cursory account of the various sul- 
phurets of copper, it may easily be inferred, that there exist 
many species of this substance, which have not yet been 
