PYRITE FROM CORNWALL, LEBANON COUNTY, 



PENNSYLVANIA. 



By CHARLES TRAVIS. 

 {Received June 22, igo6.) 



Several varieties of pyrite have been described from the Corn- 

 wall magnetite mines. Dr. Carl Hintze^ mentions three, — (i) a com- 

 bination of (hi) and (100) without a reference; (2) a combination 

 of (100), (hi), (210), (321), (432), (221) containing 2 per cent, 

 cobalt ;2 and (3) another variety for which no forms are given, but 

 whose analysis shows 2.39 per cent, copper.^ 



The present paper is a crystallographic study of two varieties of 

 Cornwall pyrite, which will be called Type I and Type II respec- 

 tively. Type II is identical with the second variety of Hintze, the 

 cobaltiferous ; a rough analysis showed i per cent, cobalt, and all of 

 the above given forms except (432) were found. Type I, on the 

 other hand, shows no copper nor cobalt, and cannot be identified with 

 any of the above. Apparently it has not been described before. 



Occurrence.^-Ty^t II occurs scattered through the ore body 

 itself. Crystals of this type grow in cavities in the magnetite, or in 

 what apparently once were cavities. Byssolite and chlorite are com- 

 monly found with them. Where the ore is lean, the pyrite crystals 

 are more numerous and are arranged roughly in layers. 



The magnetite rests against limestone, which is altered at the 

 contact. Just beyond the contact, in the limestone, Type I occurs, 

 certain thin layers in the rock near the contact and parallel to it 

 being rich with pyrite of this type. The crystals are so crowded 

 in these layers that they largely interfere with each other's growth 

 and perfect crystals are rare. 



^"Handbuch der Mineralogie," Vol. I (1900), p. 964- 

 'Blake in Dana's "Mineralogy" (1868), p. 63. 

 'Booth in Dana's "Mineralogy" (1855), p. 55- 



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