SHALE. 



463 



E. Quartziferous ; and passing into flaggy sand- 

 stone. 



F. With rounded nodules of trap or other foreign 

 fragments imbedded : occurs in Pabba and Sky. 



Pyrites is not unfrequently imbedded in 

 shale. It then sometimes becomes 



G. Aluminous schist or alum slate: forming an 

 aluminous saline efflorescence on exposure to air, par- 

 ticularly if accompanied by heat and moisture, and 

 thus generally falling to pieces. 



Shale is also a repository of common iron 

 stone and of the septaria. 



It further often contains vegetable and animal 

 remains in great variety ; whence arise a set of 

 distinctions which will find their proper place 

 in any arrangement that may be formed of fossil 

 organized bodies, but which do not fall within 

 the plan of this work. 



Where it is in contact with trap, it often passes 

 into siliceous schist, as is noticed under that head. 



