312 MINERALOGY 



it is the most important of the copper ores. Its copper content, 

 however, varies greatly from an admixture of pyrite. 



Some deposits have arisen from magmatic segregation, and then 

 it is associated with other sulphides, as pyrite, bornite, or pyrrho- 

 tite; as a primary mineral it is disseminated through the ferro- 

 magnesian igneous rocks, especially those containing pyroxene 

 or hypersthene. It is these primary sulphides which furnish the 

 copper of the secondary deposits, in veins, etc. Of the products 

 of oxidation, derived from chalcopyrite, the sulphates of iron and 

 copper are very soluble and may be transported in solution to be 

 reprecipitated again, either close at hand or at a distance according 

 to local conditions, as chalcopyrite or in some other form. These 

 solutions may flow down along the veins from which the sulphates 

 originated, to be precipitated at lower levels by hydrogen sulphide, 

 pyrite, or other sulphides, yielding the more valuable ores of the area 

 of secondary enrichment. In this way pyrite used in the Copper 

 Queen mine, in the early days, to fill stopes is being mined at the 

 present time, it having accumulated nearly 12 per cent copper. 

 Chalcopyrite is present in nearly all ore veins contained in meta- 

 morphic or sedimentary rocks and limestones ; also reported in fur- 

 nace slags, indicating its formation by dry fusion at ordinary 

 pressures, analogous to its artificial formation in a simple fusion of 

 pyrite and copper sulphide. 



STANNITE 



Stannite. Cu 2 FeSnS 4 ; Tin pyrite ; Cu = 29:5, Sn = 27.5 ; 

 Fe = 13.1, S = 29.9 ; Tetragonal ; Type, Ditetragonal Alternating ; 

 c = .986 ; Crystals sphenoidal, very rare ; Cleavage, indistinct ; 

 Brittle, fracture uneven ; H. = 4 ; G. = 4.3-4.52 ; Color, steel- 

 gray to iron-black ; Streak, black ; Luster, metallic. 



B.B. On coal fuses and yields a white coat (SnO2) and a sul- 

 phur dioxide odor. Roasted and reduced with soda, yields malle- 

 able buttons which react with the fluxes for copper. Soluble in 

 hot nitric acid, yielding a blue solution and a white residue of tin 

 oxide and sulphur. 



General description. Crystals have been described from 

 Bolivia ; its usual occurrence is massive, granular, or disseminated, 

 variable in composition owing to the admixture of other sulphides as 

 chalcopyrite. Stai^nite is associated with cassiterite in the Corn- 



