GUIDE TO THE MIXEKALOGIC COLLECTION'S 



37 



It is rarely found in distinct hexagonal crystals of tabular 

 habit, the most common form of occurrence being as a massive 

 metallic mineral of a bronze color possessing to a varying degree 

 the property of attracting the magnet. It differs from pyrite, 

 bornite and niccolite in color and in the magnetic property men- 

 tioned above. 



Pyrrhotite occurs in gabbro and other igneous rocks and in 

 schists; it is also found in meteorites. It is very widely dis- 

 tributed. The principal American localities are Sudbury Can. 

 and Lancaster Gap Pa. at both of which places it is mined for 

 the nickel it contains. A deposit of pyrrhotite was formerly 

 worked at Anthony's Nose, Westchester co. N. Y. 



Bornite (purple copper ore) 



Bornite is a sulfid of copper and iron of variable proportions, 

 the massive variety being probably a mechanical mixture with 

 chalcocite. The crystallized mineral seems to conform quite 

 closely to the formula which gives 28.1$ sulfur, 55.5$ copper and 

 16.4$ iron. 



The crystallized specimens show isometric forms with a cubic 

 habit. The massive varieties have a granular to compact struc- 

 ture. The mineral is characterized by a metallic luster and a 

 dark copper-red, pinchbeck-brown or purple color which tar- 

 nishes rapidly to iridescence. 



Bornite occurs associated with the other copper minerals in 

 Cornwall (crystalline), Chile, Peru, Bolivia, Mexico and Canada 

 and in the United States at Bristol Ct. and near Wilkesbarre 

 Pa. 



It is mined for copper. 



Chalcopyrite (copper pyrites) CuFeS 2 



Chalcopyrite is a sulfid of iron and copper in the proportions, 

 35# sulfur, 34.5$ copper and 30.5$ iron. Variations from these 

 proportions are often due to pyrite mechanically intermixed in 

 the massive varieties. 



The tetragonal crystals of chalcopyrite belong to the sphe- 

 noidal group and when in simple, unmodified forms resemble 

 isometric tetrahedral types. Modified crystals such as those 

 given in fig. 166, 167, however, clearly show the true symmetry 



