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Mineralpedia Details for Gratonite

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Gratonite

Gratonite

Named after Louis Caryl Graton, former Professor of Mining Geology at Harvard University in Massachusetts, USA. Gratonite is a rare mineral that can be found in Peru, Cuba, Poland, Bulgaria, Germany, Switzerland, the Isle of Man, Spain, Namibia, and Japan. It occurs in vugs in hydrothermal copper deposits. Associated minerals include realgar, pyrite, sphalerite, pyrrhotite, aresenopyite, enargite, tetrahedrite-tennantite, jordaite, canfieldite, and hutchinsonite.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/gratonite.pdf

Formula
Pb9As4S15 
Crystal System
Trigonal 
Cleavage
None, None, None 
Luster
Metallic 
Color
lead gray, dark lead gray 
Streak
black 
Class
Trigonal - Ditrigonal Pyramidal 
Fracture
Brittle 
Hardness
2.5 
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GRATONITE from Cerro de Pasco, Pasco dept., Peru

GRATONITE
            from Cerro de Pasco, Pasco dept., Peru
Special Info
Type Locality,Phillips Collection

Excellent miniature Gratonite with dozens of superb stout prismatic crystals, the cross-sections are hexagonal and the terminations are rhombohedrons - you'll see three faces making up the trigonal pyramid, but six sides parallel to the c-axis making up the hexagonal prism. This is the comon crystal form of Gratonite.

Click thumbnail images for larger view.

Gratonite from Excelsior mine, Cerro de Pasco, Pasco dept., Peru

Gratonite
            from Excelsior mine, Cerro de Pasco, Pasco dept., Peru
Special Info
Type Locality

Sharp metallic silver trigonal crystals to 2mm. 

Click thumbnail images for larger view.

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