314 



MINERALOGY 



all of which are soluble in water and when in solution react both as 

 solvents and reducing agents, attacking other minerals. The ulti- 

 mate result or products of oxidation are the hydroxides of iron, 

 limonite and gothite, and the oxide hematite, all of which often 



FIG. 402. Pyrite Crystals. 



occur as pseudomorphs after pyrite. Secondary pyrite is formed 

 from the sulphates of iron carried in the circulating ground waters ; 

 the organic matter contained in shales, coal, and fossils reduces 

 these solutions and the iron is precipitated as pyrite. 



Pyrite is mined commercially at Davis, in the Berkshire Hills, 

 Massachusetts, where it is found in a crystalline schist ; in St. 

 Lawrence County, New York ; these deposits are associated with 

 limestone and schist. In Eastern Virginia large lenses of pyrite 

 occur associated with chalcopyrite, sphalerite, galena, and pyrrho- 

 tite ; these deposits yield one half of the quarter of a million tons 

 produced in the United States annually. It is also mined in smaller 

 quantities in Georgia, Alabama, and California. All the pyrite 

 mined is used in the production of sulphuric acid. Pyrite may be 



