186 Decomposition of Iron Pyrites. 



No. 31. Pyrite. French Creek, Pennsylvania. Pale brass- 

 yellow brilliant octahedra, often greatly modified and distorted 

 by faces of the pyritohedron ; in byssolite and calcite. Decom- 

 position : rare traces of iridescence on some crystals. 



No. 32. Pyrite. Dutch Girl Mine, Cochise County, Ari- 

 zona. Glittering yellow grains, associated with galenite, chal- 

 copyrite, quartz, etc.; reported to contain 140 of silver and gold 

 per ton. Some cubes are distinguishable, polished, sometimes 

 striated, with slight modifications of the octahedron and pyrito- 

 hedron ; pale brass-yellow and splendent on fracture. Decom- 

 position : a yellow tarnish, partly iridescent or blue. 



No. 33. Pyrite. Cornelia Mine, Utah. Pale brass-yellow 

 and splendent cubes, well striated and with the solid angles 

 modified by the octahedron ; imbedded in finely granular pyrite 

 and white quartz. Decomposition : a slight dulling of lustre on 

 some crystals, with occasional slight iridescence and a blue or 

 red tarnish. 



No. 34. Pyrite. Central City, Colorado. Well striated 

 cubes, with faces sometimes curved, and with angles modified 

 by faces of the octahedron and pyritohedron ; pale brass-yellow 

 and splendent on fracture. Implanted on drusy quartz. De- 

 composition : a dull bluish iridescent tarnish on many crystals. 



No. 35. Pyrite. Rossie, New York. Sharply defined cubes, 

 Avith indistinct striation, and with solid angles modified by a 

 minute plane of the octahedron, pale brass-yellow and bright on 

 fracture ; imbedded in reddish white calcite. Decomposition : 

 a slight iridescent yellow tarnish. 



No. 36. Pyrite. Hassayampa District, Yavapai County, Ar- 

 izona. Irregular grains and tiny cubes, sometimes striated and 

 with slight modifications by the pyritohedron ; in grayish white 

 quartz. The mineral is pale brass-yellow and splendent, and 

 reported to contain $50 of silver and gold to the ton. Decom- 

 position : no trace visible. 



No. 37. Pyrite. Fortune Mine, Yavapai County, Arizona. 

 Massive pyrite and brilliant yellow crystals, with galenite in 

 quartz. Strongly striated cubes with modifications of the 

 pyritohedron, and some pyritohedra. The ore is reported to 

 contain $200 of gold and silver per ton. Decomposition : a deep 

 yellow tarnish common. 



