50 DOMAIN III. ARGILLACEOUS. 



among the Andes in South America, and in 

 many other metallic regions. This is in general 

 very far removed from siderous slate, which is 

 commonly quarried as valuable in architecture; 

 being less ferruginous, and far more coarsely 

 schistose, so as sometimes to be even confounded 

 with grauwack. The necessity of new denomi- 

 nations in mineralogy is also^apparent from this 

 example; for while we are told by Mr. Kirwan 

 that the Andes chiefly consist of primeval blue 

 argillite, one would expect an universal reposi- 

 tory of slates for architecture; while in fact none 

 such appear, and the substance is a coarse clay 

 slate, slightly impregnated with iron. In like 

 manner Mr. Jameson must mean the present 

 substance when he gives us the following in- 

 formation. 



" Clay slate is one of the most metalliferous 

 of the primitive rocks. It contains many of the 

 venigenous formations that occur in the preced- 

 ing primitive rocks, as tin, lead, cobalt, and 

 silver. Very considerable metalliferous beds also 

 frequently occur, and these contain copper py- 

 rites, red copper ore, copper green, copper 

 azure, malachite, iron pyrites, magnetic pyrites, 

 glance cobalt, grey cobalt ore, arsenic pyrites, 

 blend and lead glance. Gold also occurs in this 

 formation, and it is said also cinnabar. 



