bis MINERALS OF CHILE. 



were massive, of a brass -yellow color, metallic luster, fresh 

 fractured surfaces tarnishing readily. In fact it possesses all 

 the known characteristics of this mineral as found elsewhere. 

 Its composition when perfectly pure is 



Sulphur 35.05 



Copper... 34.47 



Iron 30.48 



100.00 



Several specimens examined gave 



12 3 4 



Sulphur 33.05 37.22 



Copper 36.60 33 67 31.02 35.01 



Iron 29.33 28.56 



98.98 99.45 



Its formula is Cu 2 S+Fe 2 S 3 . 



This mineral is rarely found in granite, but often in horn- 

 blendic and porphyritic transition rocks, accompanied by iron 

 pyrites, magnetic iron, asbestos, quartz, and various species of 

 clay; very rarely with carbonate of lime. The most important 

 mines yielding the copper pyrites are Carrisal, Atacama, and 

 Higuera, Brillador, Tambillos, etc., in Coquimbo. 



ARSENICAL GRAY COPPER. 



Gray copper appears not to be found very abundantly in 

 Chile. There are, however, three varieties of it; one of which 

 contains quite an amount of mercury, another having the com- 

 position of ordinary gray copper, while a third abounds in 

 arsenic. They all three possess the ordinary physical charac- 

 ters of gray copper; namely, a steel-gray and iron-black color, 

 with metallic luster, rather brittle; hardness, 3 to 4, with specific- 

 gravity varying from 4.5 to 5. No specimen of this variety 

 was obtained. It is found at San Pedro Nolasco, and its com- 

 position, as made out by M. Domeyko, is 



Copper 48.5 



Iron 4.8 



Zinc 2.3 



Silver 3 



Arsenic 11,4 



Antimony 6.4 



Sulphur 26.1 



99.8 



