152 PHYSIOGRAPHY. 



lo wish -grey. Streak white, acquires some lustre. 

 Translucent ... opake. 



Sectile. Hardness = 3-0. Sp. Gr. = 2-507 of a 

 greenish-black crystallised variety ; = 2-560 of 

 an oil-green, translucent one. 



Compound Varieties. Massive : composition 

 granular, impalpable. Varieties of this kind pre- 

 sent also red, brown, black, yellow, and grey 

 colours, in different ^veined, spotted, and other deli- 

 neations. The purer varieties sometimes possess an 

 indistinct slaty structure. 



The regular forms have been observed in a blackish- 

 green variety, the locality of which is unknown. Serpentine 

 is said to occur crystallised in the Tyrol. Imbedded crys- 

 tals, the prismatic form of which, however, is nearly obli- 

 terated, occur in the weisstein of Penig in Saxony. Ser- 

 pentine often contains crystals and grains of octahedral Iron- 

 ore, which must be well attended to, if we determine its 

 hardness and specific gravity. 



Serpentine is generally divided into two subspecies, the 

 common and precious Serpentine, the latter of which again 

 comprises a conchoidal and a splintery kind, distinguished in 

 colour, fracture, and transparency. It hardens on being 

 exposed to fire, and melts only with great difficulty on 

 the edges. According to JOHN, it consists of 



Silica 42-50. 



Magnesia 38-63. 



Alumina 1-00. 



Lime 0-25. 



Oxide of Iron 1-50. 



Oxide of Manganese 0-62, 



Oxide of Chrome 0-25. 



Water 15-20. 



Serpentine forms mountain masses and beds in primitive 



