TAB. XLI. 



S I L E X quartzum primitivum. 

 Primitive crystallized Quartz. 



Class 2. Earths. Order I. Homogeneous. 

 Gen. 6. Silex. Spec. 1. Quartz. 



Div. 1. Crystallized. Far. 1. Primitive. 



Gen. Char. Rough and harsh to the touch. So- 

 luble in the "two fixed alkalis ; but in no acid but 

 the fluoric, except (as some think) when in com- 

 bination with an alkali, much diluted with water; 

 also soluble in 1000 times its weight of water. 



Spec. Char, Nearly uncombined. Burns to. an 

 opaque white. Spec. grav. 2.64 to 2.67. Kinv. 



Syn. Quartz. Kirw. 1. 242, 



JTauy says that the primitive crystal of Quartz is the 

 slightly obtuse rhomb, measuring 94° 40' and 85° 5Q'. He 

 does not seem to have met with a specimen. Mine, which 

 is formed in a variegated flint, from Lewisham in Kent, 

 showing only one end of the rhomb, agrees with this de- 

 scription, as the primitive : some of them show signs of 

 the other three faces, approaching the double hexaedral py- 

 ramids. See the left hand figure. 



Silica when transparent and crystallized is commonly 

 called Ouartz, Rock Crystal, or Mountain Crystal ; the purest 

 are generally colourless, and often very brilliant. They were 



