90 THE MINERALS OF CHILE. 



Several specimens examined gave — 



Sulpliur 



- 33.03 



Copper 



- 36.60 



Iron 



- 29.33 



37.22 



33. 6T 31.02 35.01 

 28.56 



98.98 99.45 



Its formula is Cu- S + Fe^ S^ 

 This mineral is rarely found in granite, but often in hornblendic and porphyritic transition 

 rocks, accompanied hy 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, &c., 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 composition of ordinary gray copper, while a third abounds in arsenic. They all 

 three possess the ordinary physical characters of gray copper ; namely, a steel-gray and iron- 

 black color, with metallic lustre, 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 composition, as made out by M. Domeyko, is — 



. Copper -------- 48.5 



Iron 4.8 



Zinc 2.3 



Silver 0.3 



Arsenic - - - - - - - 11.4 



Antimony ---.-.. 6.4 



Sulphur ---.--. 26.1 



99.8 



Mercurial Gray Copper. — This is found in some of the mercurial mines of Chile in small 

 amorphous masses, disseminated in a quarter gangue, accompanied by the blue carbonate of 

 copper and a red earthy substance of deep red color, ajjparently an antimoniate of mercury. 

 This also has been analyzed by Domeyko, with the following result — 



Antimony - - - - - - - 20.7 



Iron -------- 1.5 



Zinc -------- trace. 



Copper -------- 33.6 



Mercury ...-.-- 24.0 

 Sulphur 20.2 



100.0 



Aniimonial Gray Copper. — This is the common form of gray copper, and several specimens 

 were brought home by the expedition ; it contained but a small amount of silver, as seen by 

 the following analysis — 



