130 Fossils. 



quartz. It is granulated, being composed 

 of sir. all grains of quartz, cemented toge- 

 ther, but which have very little adhesion. 



Fehpar is inferior in hardness to 

 quartz. It fuses by the action of heat, 

 and forms white enamel. It is one of 

 the constituent parts of porcelain. 



We may mention, under this class, ad- 

 amantine spar, which approaches near to 

 the preceding in its appearance and frac- 

 ture, but which differs from them con- 

 siderably, by its great hardness, its form, 

 and gravity. It is so exceedingly hard, 

 thai it may be employed to cut the dia- 

 mond. 



Flint is a stone * which is so hard as to 

 strike fire with steel, Among the dif- 

 ferent \ rid of flints, some change their 

 colour according to the directions of the 

 rays of light, and others do not. Of the 

 former there are three, the opal, the cat's- 

 eye and iheji.s/i-et/e. 



The kinds of flints which do not change 

 their colour according to the direction of 

 the rays of light, exhibit tints of more or 

 less brightness, and are susceptible of a 

 fine polish. We are acquainted with 

 eight kinds of them, viz. common Jtint^ 



