334 



Another spe- 

 aes 



SULPHURET O** LEAD, COPPER, AND ANTIMONY 



In this case perhaps it would be necessary to make a 5th 

 species among the sulphurets of copper of an ore, which 

 was formerly very plentiful in Cornwall, but is now become 

 rather scarce, and which probably differs from the preceding 

 species by a more or less considerable degree of oxidation in 

 the iron. This ore is of a dull yellow colour, inclining a little 

 green. Its fracture is smooth and dull, and sometimes a 

 little conchoidal. Its grain is extremely fine, and frequently 

 even imperceptible to the eye. Its texture consists of 

 parallel layers, very thin, and distinguishable only by the 

 assistance of a lens, but easily separated by a stroke of the 

 hammer. This ore has never exhibited to me any crystalline 

 form ; but it is frequently mamillary, much like the martial 

 hematites. Its surface is commonly smooth, a good deal 

 like that of a metal which has lost its polish. Its specific 

 gravity is 4*157: consequently a little greater than that of 

 the preceding yellow sulphuret of copper and iron. Its 

 hardness is nearly the same. If scratched with a knife, the 

 part scratched appears smooth, and acquires a metallic 

 lustre. On decomposition the surface frequently assumes 

 various colours, but less lively and brilliant than those of 

 the lamellar yellow sulphuret. At other times its surface 



This division 

 proposed as a 

 standard. 



good deal the look of an antique bronze, and the more so 

 as it is often partially covered with malachite. This species 

 is frequently mixed with simple sulphuret of copper, 

 a phasnomenon by no means so common in the yellow species 

 which I have just mentioned above. 



This division of the sulphurets of copper, being once 

 adopted, might be considered as a standard, to which we 

 might refer all the numerous varieties, that exhibit no marks 

 of crystallization; arranging them under one or other of 

 these species, according to the manner in which their es- 

 sential component parts are proportioned. We might then 



from St. Bel and Baigorry, which I have noticed. In these analyses 

 given in the Journal des Mines, No. 122, the author says expressly, 

 that the iron in these yellow sulphurets was in the metallic state; 

 while in two other analyses made of varieties of the simple sulphuret 

 of copper from Siberia, which were probably in amorphous masSes 

 and contained iron, he says the iron was in the state of oxide. 



place 



