GEOLOGY OF CENTRAL INDIA. 



67 



is surely not going too far to say, that tliese causes might have operated 

 most powerfully in modifying the external characters of rocks. 



The Argillaceous Schists, with their accompanying Greenstone 

 Schists, Greenstones, and Chlorite Schists, next claim our atten- 

 tion. The argillaceous schists vary much in their texture. From the 

 siliceo-argillaceous schists, which pass into the more slaty varieties of 

 quartz rock, to a schist of a loose friable texture, we have a regular gra- 

 dation. Several varieties of argillaceous schist have been described be- 

 fore (see paper on the Geology of the route from Baroda to Uclayapur,) 

 together with the rocks with which they are associated. They are very 

 generally of a dark grey color, and many of them approach to the nature 

 of roofing slate. These last are generally of a bluish color — other va- 

 rities are also bluish, but are soft and friable with a slightly greasy feel, 

 the color depending on copper^ — others are black, making an indistinct 

 mark on paper, while others are light grey, buff, fawn colored, and 

 greenish. The latter pass sometimes into chlorite schist, and at others 

 into greenstone schist. Many of them have mica disseminated through 

 their substance, and these last pass into micaceous schist, while others 

 have a distinct greasy feel, and the latter, in one situation, I have seen 

 passing into w^ell marked talcose schist. This last rock does not 

 appear to be of abundant occurrence in this district. The instance 

 alluded to was discovered in the boundary ranges of the valley. The 

 talco-argillaceous schists, or those which have a distinct greasy feel, 

 are, however, common. To the above, the cede: schiste of the French 

 may be added, which occasionally presents itself. Thin lamince, of a 

 whitish colored limestone, in small patches, being disseminated through 

 a basis of argillaceous schist. This forms a calcareo-argillaceous schist. 



The argillaceous schists frequently resemble the greywacke schists, 

 as commonly described, and these again pass into greenstone schist and 



