Ufl MITALLIC SUI.PHURETS. 



The native, fcaly, flexible orpiment melts quietly, and fcrm<* 

 a vitreous, red, tranfparent mafs, refcinbling realgar, and un- 

 alterable by the action of charcoal. There may exift natural 

 fulphurated oxides of arfenic, but certainly thefe are not fuch 

 as are formed by an elevated temperature. The native real- 

 gar of Ronda in Andalufia, is alfo a metallic fulphuret with- 

 out oxigen. 



Sulphuret of Copper. 



The fulphuret of copper exhibits a fecond inftance in tlie 

 mineral kingdom of fulphurets with a furcharge of fulphur. 

 Characters of As the lights of analyfts have hitherto been wanting, in 



per*! UrCt ° C ° P " or ^ er to P omt out to minerklogifts the real characters of this 

 fulphuret, they have always) defcribed it in an imperfect man- 

 ner, or confounded it with other mineral productions. In its 

 pureft ftate, its colour is always a deep blue, violet, or mixed 

 with the copper tinge of indigo, if rubbed with a fmooth fub- 

 france. Its colour is liable to be difguifed by a mixture of 

 carbonate of copper, red oxide of iron, &c. But when we 

 feparate thefe by folution, the fulphuret is reftored to its real 

 colour. 

 Variations from More commonly the fulphuret of copper is difguifed by its 

 unpunty. intimate combination with the other metallic fulphurets. 



Combined, for example, with the fulphuret of iron, it affords 

 the copper-coloured pyrites, in which the exiftence of the 

 blue fulphuret may eafily be demonstrated. 



If with thefe two fulphurets, confidered as the bafe, are 

 combined thofe of antimony, lead, arfenic, mercury, filver, 

 zinc, &c. each feparately, there remits a feries of ores of 

 copper, rendered grey by as many different metals, but which 

 do not on that account, as mineralogies believe, neceffarily 

 contain filver. 

 Compound ores ^ r w ^ tn tne tvvo ^ r ^ fulphurets we combine in idea the 2d, 

 of copper. 3d, 4th, and 5th of thefe which we have juit mentioned, we 



have in thefe combinations as many complicated ores of cop- 

 per. Amongft thofe which are brought from America, there 

 are others likewife compounded with native filver, the car- 

 bonates of iron, manganefe, fulphate of barytes, &c. Such 

 are the different fpecies of mineralizations which mineralogies 

 have indifcriminately comprehended under the two claffes of 

 white and grey ores of copper. 



The 



