SULPHURET OF LEAD, COPPER, AND ANTIMONT. 327 



per, agreeing at the same time with respect to the propor- 

 tion in which it enters into this compound, is I believe as 

 complete a demonstration, as chemistry can furnish : at 

 least if there be any errour in it, the errour must be proved. 



The majority of ores in the sulphuretted state, of which Ores of copper 

 copper constitutes a part, being of a gray colour; these r asil LT n " 

 ores being very numerous ; in some of them the copper be- 

 ing merely interposed ; and in the greater number of those 

 of which it is a component part, being commonly inter- 

 mingled with different metals, most of them sulphuretted 

 likewise: nothing is more difficult, than to distinguish these 

 ores, so as to refer each to the principal and particular 

 type, to which it belongs. 



Among the different species, to which these ores may be Fahlertz. 

 referred, it has uniformly appeared to me, that what the 

 Germans call fahlertz belongs to the gray species that crys- 

 tallizes in regular tetraedra. But this species, in which the Very liable to 

 copper in the sulphuretted state is in pretty large quantity, extraneous 

 is at the same time one of those most subject to admit foreign 

 substances by the interposition or juxtaposition of their mole- 

 cules. As I have already said in my first paper on endellion, 

 presented to the Royal Socisty, it appears to me unquest- 

 ionable, that the essential component parts of the gray 

 tetraedral sulphuret of copper are copper, iron, and sul- 

 phur; and the analysis, which I have there said was made 

 by Mr. Chenevix of a variety from Cornwall in well de- 

 fined crystals, in which he found nothing but these, in 

 the proportions of copper 0-52, iron 0-33, and sulphur 0-14, 

 seems sufficient to prove that these substances are thus pro- 

 portioned in this ore. 



The author of the paper, when he gives fahlertz as the Mr. Smithson'* 

 second component part of endellion, considered as the P r0 - ^riet ^amon*" 

 duct of a binary combination, says that it is composed of the antimonial 

 23f sulphur, 50 antimony, and 26f copper; a composition ores ' 

 that would constitute a variety among the antimonial ores, 

 and has nothing to do with that I have just given. But as 

 it differs materially from all the very numerous analyses, 

 that have been made of different varieties of gray copper 

 containing antimony, it must be the result of the author's 

 own observations, aud a particular series of experiments, 



which 



