Mineralogy of Southern India, 211 



or not, of a very firm structure. It is very rare, and forms 

 a small hill near Arnagherry, west of Salem, not far from 

 the banks of the Cavery. A similar rock is called quartz rock 

 by Bakewell, and classed as mica schist, and as primary 

 sandstone by Macculloch. 



Limestone. 



This is not a correct name for this rock; but as limestone 

 of any kind is very rare in Southern India, as a formation 

 (excluding kunkur of course) among the primary rocks, it will 

 do very well for the present, while no distinctions by definition 

 are required. It is properly a perfect granite ; of a firm, solid, 

 durable structure ; and possessing a perfect cuboidal cleavage, 

 and might serve as a building material. It is a binary granite, 

 formed of quartz and of carbonate of lime in acicular crystals, 

 confusedly aggregated. The lustre is a beautiful pearly 

 white, and so perfectly resembles binary granite, that I was 

 only induced to try it with an acid, in consequence of a 

 marked peculiarity in the appearance of the crystals, which I 

 am unable to define. It occurs in blocks at the southern end 

 of the Tally Mally, in the southern extremity of the Salem 

 district, close to the Cavery. I have not seen it in sites. 

 Ainslie seems to allude to this rock, but does not mention 

 where it is found. I have not met with a definition of any 

 similar limestone by European penologists. This rock is 

 readily disintegrated by muriatic acid, leaving the crystalline 

 grains of quartz separated. 



Wackc, 



is properly applied to a soft earthy rock of the Trap family, 

 or a basalt: but as I cast aside all such theoretic distinctions, 

 I apply the term to a similar mineral occuring extensively 

 in my schistose series in Southern India, and which seems 

 to form the subsoil from which the earth of some of the 

 most fertile tracts is derived. Its fracture is sometimes even, 



