150 ON METALLIC^ SULPHURETS. 



and iron. This opinion appears to me very probalile : though 

 perhaps we have not sufficient grounds to assert, that the 

 sulphuret of iron exists in it in the same state of combina- 

 tion as that, which constitutes native iron pyrites. 

 Analysis of Mr. Chenevix obtained from a specimen of copper pyrites 



Mr. Chenejnx gQ pg^ ^^^^ ^f copper, and 53 of oxide of iron, correspond- 

 ing to 35 of the metal. I hkewise found 30 per cent of cop- 

 per in a piece of yellow ore from Chessy. On comparing 

 these results with those above given, T was struck with the 

 proportion that exists between the elements of a mineral 

 generally considered as varying greatly in its composition. 

 The difficulty of distinguishing it from iron pyrites may 

 have contributed to this opinion : but I am inclined to tliink, 

 that, when copper pyrites is completely homogeneous, and 

 This confirms not decomposed, its composition is the same, from whatever 

 the idea of its •. . i ^ • j i ^i . •. , • i 



uniformity. ®^^ *^ "^ obtamed ; and that it may be considered as a 



mineralogical species, ascertained and determined by che- 

 mistry. 



This however is but a simple conjecture, on which nothing 

 positive can be said, till we have a greater number of analy- 

 ses made on well marked specimens free from any mixture. 



XIT. 



Analysis of a Carbonate of Lime from Pesey\ by Mr, Ber- 

 THiER, Mine Engineer*, 



The cartonate J» HE carbonate of lime from the mine of Pesey is found 

 des>-ribed. in geodes grouped comfusedly with quartz, and sometimes 

 with lenticular polishing spar. Its specific gravity is 2*<)7. 



Its figure is that of the primitive rhomboid of common 

 carbonate of lime. It may be split with great facility, and 

 divides in the direction of its longer diagonals. All the faces 

 are covered with strioe in this direction. 



Its hardness is much greater than that of common car- 

 bonate of lime, which it scratches. It even scratches arra- 

 gonite. The pieces found on the heaps of rubbish, that 

 Jjgive remained long exposed to the air, have the brown co- 



« Annales de Chimie, vol. LVIH, p. 87. 



lour 



