Mineralogy of Southern India. 205 



recognised by a lens ; yet cohering after the peculiar manner 

 of granite rocks. Is a graduation from the prevailing Horn- 

 blendic granite of Southern India, and is generally found 

 associated with micaceous varieties. Is found near Ryacot- 

 tah, and is so tough as to require blasting to separate the 

 blocks. Has a perfect cuboidal cleavage, and if polished 

 would form a very beautiful building stone. 



Pegmatite. 



A binary compound of crystalline quartz and felspar, more 

 or less saccharine. It differs from binary granite in the 

 felspar, not forming resplendent crystals, but having an are- 

 naceous or an earthy appearance. It forms extensive beds 

 in the schistose series of rocks of Southern India, but has 

 no regular cleavage, and is generally so loose in aggregation 

 as to break readily to pieces, and sometimes crumbles down, 

 so as to be used as a road-making material. The term Peg- 

 matite was first used by the French geologists, as applied to 

 binary granite ; but, as Dr. Benza has used the term in the 

 same sense as I have now defined it, I have therefore pre- 

 served it. Dr. Boase, (Primary Geology, page 203,) uses the 

 term as synonymous with graphic granite, and classes it with 

 the schists of Cornwall, with which he says it graduates. Dr. 

 Macculloch (Rocks, page, 340) describes it as a variety of 

 " red primary sandstone," but his theoretic distinction I do 

 not allow to be correct, unless people choose to consider my 

 " schistose series" as being of derivative origin; but in itself 

 or its associations, the structure of the rock is totally differ- 

 ent from the " coherence" of the composing materials of the 

 secondary sandstones. In Southern India, it seldom is found 

 without some slight admixture of Mica or Hornblende. 



Eurite. 



This is a French term, and applied to the Weiss-stein 

 or white-stone of Werner. It was first used in Indian petro- 

 logy by Dr. Benza, but he has not been very precise in his 

 application of the term : and though I have visited much of 



