486 LIST OF MlNEJlALS, THEIR 



Pyrgom ; Sahlite ; Vulcanite ; the green prisms 

 which accompany the Jenite from Elba, and which 

 have been called Hornblende ; the white Pyroxene 

 from New York ; and Bournon's yellow Topaz from 

 Vesuvius. An oblique rhombic prism, P on M 

 orM', 101; M oa M, 87 5.' 



Several of these varieties, particularly the Sah- 

 lite, have a cleavage transverse to the axis of the 

 prism, which the others have not. But this cleav- 

 age appears to take place only where some foreign 

 matter is interposed between the laminae of the 

 crystals ; for the same crystals which may be sepa- 

 rated at one of these apparent junctions, cannot 

 be cleaved in the same direction in other parts of 

 the prism. 



granular; Coccolite. 



amorphous. 



fusible. The cleavages and the angles of this variety 

 are similar to those of Pyroxene, as nearly as can 

 be determined by the reflective goniometer, from 

 planes which are not very bright; yet from its 

 ready fusibility, it may possibly be a distinct 

 species. I have observed this variety differing in 

 colour and external appearance from two localities, 

 from Sweden, imbedded in Quartz ; Euchysiderite. 

 Greenland, accompanying Eudyalite. 



Q 



QUARTZ. 



crystallised. An obtuse rhomboid, P on P', 94 15'. 



colourless ; Rock crystal ; Dragonite. 



black. 



brown ; Smoky quartz. 



red ; Compostella quartz ; Ferruginous quartz. 



yellow ; transparent. 



opaque, ferriferous ; Eisenkiesel. 



violet to purple ; Amethyst. 



green ; prase, 

 laminar ; milky. 



rose. 



acicular radiated. 



iibrous. 



granular. 



yellowish green ; Cantalite. 



arenaceous. 



. flexible. 



