210 Mineralogy of Southern India. 



beds ; and it is characteristic of this formation, for it never 

 forms hills or mountains, or any extensive formation of ele- 

 vated points. Occurs as wall-sided dykes in the schistose 

 series near Anchetty, west of Ryacottah, and in Congoondy, 

 and also on the top of the Naiknairy ghaut. I may assert, 

 I believe, that wherever I have seen it, it is accompanied 

 with evidences of igneous action, slides, injections, dykes 

 and metamorphic action on the adjacent rocks. I cannot 

 help thinking it probable, that the enormous masses and for- 

 mations of porphyry " said to be found in Norway," are not 

 of felspar porphyry, but of porphyritic granite, like the 

 Yailgerry hills of Salem perhaps. Felspar porphyry never 

 has a cleavage, and is never used as a building stone in 

 Southern India. 



Quartz Rock 

 is found in great profusion in beds and dykes in the schis- 

 tose series, and is commonly used for fluxing into glass 

 with the mineral carbonate of soda, by the bangle maker. 

 It is sometimes found embedded in granite, in irregular 

 masses of 3 or 4 inches thick, but is not common. It is some- 

 times found forming small hills, but is always cracked, and 

 so separated by irregular divisions, that a solid piece, more 

 than 4 inches thick, can seldom be procured. The varieties 

 it forms are — semi-transparent, rose, smoky, fat, milk, sac- 

 charine, wax ; but of all these, milk quartz most commonly 

 occurs. Is found as veins, contorted, vertical and horizontal, 

 both in the ferraceous series and in the beds of the schistose 

 series ; but though the veins are sometimes of considerable 

 width, (tabular veins) yet they are always separated into 

 cracked prismatic pieces, with the irregular surfaces exactly 

 answering to each other, (i. e. in sites.) 



Granular Quartz Rock. 

 Formed of an aggregation of small crystals of white 

 quartz, with a small quantity of black mica, forming an 

 imperfect lamination, and the whole cohering rather loosely, 



