156 DOMAIN II. SILICEOUS. 



small veins of white quartz. Of this the basanite, 

 or Lydian stone of Werner, is accounted only a 

 diversity ; but many regard it as a black jasper, 

 and as all the jaspers are impregnated with iron, 

 it w r ould be truly surprising if there were no black 

 jasper. According to Mr. Jameson, the flinty 

 slate of Werner not only occurs in considerable 

 beds in primitive slate, but also, like quartz, forms 

 entire mountains. 



It appears by the French writers to have been 

 sometimes confounded with a fine trap or basalt. 

 Latterly siliceous schistus has been understood to 

 present various colours; and when it occurs in 

 grauwacke slate, is regarded as a transitive rock. 

 The primitive is said to underlay the granite of 

 Mount Sorel, in Leicestershire. 



chert. Aspect 2. The chert of the English* chiefly 



occurs in layers in lime-stone, and sometimes con- 

 stitutes a mass of petrified shells. 



Dark grey chert, with lime-stone, in layers, 

 from Derbyshire. 



Reddish chert, with lime-stone, from France. 



Brown chert, full of petrified shells, from Der- 

 byshire. 



In bowls, with concentric layers, brown and 

 grey, from Vaucluse. Saussure, 1546. 



* Chertz of some counties, which seems related to quartz. 



