Wakabayashilite

Composition: (As,Sb)11S18

Crystal System: Hexagonal

Color: Golden yellow

Type Locality: Nishinomaki Mine, Gunma Prefecture, Japan

Wakabayashilite is a very rare mineral found in low temperature environments.  It predominantly occurs with other arsenic minerals such as orpiment and realgar in high-arsenic gold deposits.  Although wakabayashilite crystallizes in the hexagonal system, it forms long, needle-like crystals with a silky luster.  These are very distinct, but even so were originally thought to be orpiment because of their color. 

First scientifically described from the Nishinomaki Mine, on Honshu Island, Japan, in 1972, the mineral was first found at the White Caps Mine at Manhattan, Nevada prior to 1930.  In a 1930 paper in the American Mineralogist, Charles Palache and Dave Modell mentioned 'orpiment' occurring as 'slender needles of a clear yellow color' from the White Caps Mine.  Miners referred to this mineral as 'hair orpiment' and as such it was considered it a variety of orpiment until the 1972 paper describing it as a new mineral.  Specimens in old collections from Manhattan may still bear the 'hair orpiment' designation, but are in fact wakabayashilite.  

 

Wakabayashilite on calcite, from the White Caps Mine, Manhattan, Nye County, Nevada.  The pocket is 9 centimeters wide, with individual crystals to over 3 centimeters.  This specimen is thought to be the finest wakabayashilite in existence.  Photo by Ben Schumer

 
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