FREE BOOKS

Author's List




PREV.   NEXT  
|<   110   111   112   113   114   115   116   117   118   119   120   121   122   123   124   125   126   127   128   129   130   131   132   133   134  
135   136   137   138   139   140   141   142   143   144   145   146   147   148   149   150   151   152   153   154   155   156   157   158   159   >>   >|  
tes therefore looks cloudy, except for supplies used locally, as in the territory tributary to the Great Lakes, and except for small amounts locally recovered as by-products in the mining of coal or from ores of zinc, lead, and copper. Pyrite production in the past has been chiefly in the Appalachian region, particularly in Virginia and New York, and in California. GEOLOGIC FEATURES Pyrite, the yellow iron sulphide, is the commonest and most abundant of the metallic sulphides. It is formed under a large variety of conditions and associations. Marcasite and pyrrhotite, other iron sulphide minerals, are frequently found with pyrite and are used for the same purposes. The great deposits of Rio Tinto, Spain, which produce about half of the world's pyrite, were formed by replacement of slates by heated solutions from nearby igneous rocks. The ores are in lenticular bodies, and consist of almost massive pyrite with a small amount of quartz and scattered grains and threads of chalcopyrite (copper-iron sulphide). They carry about 50 per cent of sulphur, and the larger part carries about 2 per cent of copper which is also recovered. Similar occurrences of pyrite on a smaller scale are known in many places. Pyrite is very commonly found in vein and replacement deposits of gold, silver, copper, lead, and zinc. In the Mississippi valley it is extracted as a by-product from the lead and zinc ores, and in the Cordilleran region large quantities of by-product pyrite could easily be produced if there were a local demand. The pyrite deposits of the Appalachian region are chiefly lenses in schists; they are of uncertain origin though some are believed to have been formed by replacement of metamorphosed limestones and schists. Under weathering conditions pyrite oxidizes, the sulphur forming sulphuric acid,--an important agent in the secondary enrichment of copper and other sulphides,--and the iron forming the minerals hematite and limonite in the shape of a "gossan" or "iron-cap." Pyrite is likewise frequently found in sediments, apparently being formed mainly by the reducing action of organic matter on iron salts in solution. In Illinois and adjacent states it is obtained as a by-product of coal mining. SULPHUR ECONOMIC FEATURES Sulphur is used for many of the same purposes as pyrite. Under pre-war conditions, the largest use in the United States was in the manufacture of paper pulp by the sulphite process. Mi
PREV.   NEXT  
|<   110   111   112   113   114   115   116   117   118   119   120   121   122   123   124   125   126   127   128   129   130   131   132   133   134  
135   136   137   138   139   140   141   142   143   144   145   146   147   148   149   150   151   152   153   154   155   156   157   158   159   >>   >|  



Top keywords:
pyrite
 

copper

 

formed

 

Pyrite

 

replacement

 

conditions

 
product
 
deposits
 

sulphide

 
region

FEATURES

 

sulphides

 
schists
 

frequently

 

forming

 

purposes

 

minerals

 

sulphur

 
recovered
 
mining

locally

 

chiefly

 
Appalachian
 
weathering
 

extracted

 

oxidizes

 

limestones

 
Mississippi
 

sulphuric

 

demand


valley

 

lenses

 

quantities

 

origin

 
believed
 

easily

 
metamorphosed
 

produced

 
uncertain
 

important


Cordilleran

 

apparently

 

largest

 
Sulphur
 

ECONOMIC

 

states

 

obtained

 

SULPHUR

 

United

 
sulphite