DOMAIN II. SILICEOUS. 



lision, so that, during Alpine hurricanes, 

 the torrents, rolling large fragments of rock, 

 present a singular scene of confiscation. 



MODE I. QUARTZ. 



Distinctive Texture, compact, generally uniform, some- 

 times granular, rarely laminar, in which form 

 the lustre is generally dull. 



Hardness, crystallic. Fracture, splintery, but 

 such as sometimes to resemble the conchoidal. 

 Fragments, very sharp. 



Weight, granitose. 



Lustre, glistening or shining, sometimes unc- 

 tuous. From transparent to opake. 



Colour, generally white; sometimes brown, 

 grey, yellow, red, or black. 



It sometimes composes entire mountains, and 

 abounds in those of granite, in which substance 

 it is seldom crystallised. 



STRUCTURE I. COMPACT. 



Aspect 1. Opake. A very common substance, 



but the specimens of entire mountains are rare. 



sites. Xhe mountain of Kultuck, on the south-west 



end of the lake Baikal, 350 feet high, and 4800 



long, and still broader, consists entirely of milk- 



