PHYSIOGRAPHY. 157 



Cryolite. 



3. It occurs at Przibram in Bohemia, in veins containing silver-ores, 

 along with Brown Iron-Ore, Spathic Iron, White Iron-Pyrites and 

 Calcareous Spar. It has also been found at Wheal Maudlin in Corn- 

 wall. 



CRYOLITE. " Prismatic Cry on e-Haloide . 

 MOHS. 



Primary form. Right-rectangular prism. C. 



Cleavage, parallel with P perfect, with M and T less 

 perfect, or coherent. Fracture imperfect or conchoidal. 

 uneven. 



Lustre vitreous, a little inclining to pearly upon the faces 

 of P. Color white, sometimes verging upon red or yel- 

 lowish-brown. Streak white. Semi-transparent ... trans- 

 lucent. On account of its low refractive power, it appears 

 more transparent when immersed in water. 



Brittle. Hardness = 2-5 . . . 3-0. Sp. gr.=2-963 of a 

 white variety. 



Compound Varieties. Massive : composition granular, 

 the individuals being of considerable size. 



1. It is very fusible, and melts even in the flame of a candle. Before 

 the flame of the blow-pipe, it is first perfectly liquified ; but soon be- 

 come? hard again, and assumes at last a s'aggy appearance. It is inso- 

 luble in water, though it suffers cleavage more readily after having 

 been immersed in it far some time. 



2. Analysis. 



By K LAP ROTH. By VAUQUELISF. 



Alumina - - 21-0 - .- - 24-0 



Soda - - 32-0 - - - 36-0 



Fluoric acid and \vater 47-0 ... 40-0 



3. It occurs at Arksut-fiord, (West Greenland,) in two small layers in 

 gneiss, one of which contains orjjy the white varieties, whereas the other 

 contains the colored ones, accompanied by Galena, Irjii- Pyrites, Spathic 

 Iron and Feldspar. 



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