CHRO.MITK A.XD PICOTiTK. I77 



The picotite from Vicdessos is cofTee-brown to yellowish-brown, translu- 

 cent, and shows a smooth surface in reflected light. 'J'he chromite or picotite 

 of St. Paul's Rocks is greenish-brown to brownish-yellow in color, translucent, 

 and contains in association with it and in its interior, grains of pyrite and 

 other iron ores of secondary origin. The chromite itself is here thou-'-ht to 

 also be an alteration-product. 



The mineral in the Todtmoos peridotite shows in part a pale yellowish 

 central portion surrounded and traversed by portions of a coffee-brown color 

 which fade into a surrounding black opaque exterior. Number 142 G., from 

 San Domingo, has its mineral in part colored deep coffee-brown, translucent, 

 and traversed by dark opaque bands, part of which are magnetite. The 

 mineral is in part entirely opaque. In numbers 3001 and 3002 from Colusa 

 Co., California, the picotite or chromite is yellowish-brown in part, but most 

 is opaque and gives a dull, grayish reflection. Some grains were found to be 

 partly filled with pyrite, and some are traversed by black opaque bands along 

 the fissures, while others again show a brownish surface in reflected light, 

 traversed by bluish magnetite veins. One grain had a ti-anslucent centre, 

 with a brown opaque border cut by magnetite veins. 



The mineral in the Baste schiUerfels is in part coffee-brown and in 

 part opaque. The translucent grains contain opaque portions. In this, 

 as in many of the others examined, the opacity appears to arise from, 

 and to be proportionate to, the amount of alteration in the picotite or 

 chromite. 



In the Webster (N. C.) peridotite the smaller grains are coffee-brown and 

 translucent, but the thicker interior portions are of a much darker color than 

 the edges. The larger grains are coffee-brown and translucent on their 

 edges, but opaque in the interior, and show a rough surface with a dull 

 reflection. A few of the smaller grains have the same characters. The 

 powder is coffee-brown and translucent on the thin edges. The mineral in 

 the Andestad-See rock is of a coffee-brown color in the thinnest portions, and 

 in minute grains, but the remaining portions are opaque, and give the usual 

 dull reflection. Some of the grains are cut by fissures filled with serpentine. 

 Part of the grains in the Tafjoid rock are entirely translucent and have 

 a yellowish-brown to a reddish-brown color ; part are entirel}^ opaque, and 

 have a rough surface with a dull lustre ; while part have the exteriors and 

 some of the central portions translucent, and their remaining portions 

 opaque. The Tron (Norway) rock has the centres of the grains translucent 



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