GEOLOGY OF CENTRAL INDIA. 



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granular ; 5th, a sienitic granite intermediate between snxall and large 

 granular, and principally composed of grey felspar, with which is occa- 

 sionally associated quartz and hornblende, the last in minute proportion — 

 a soft reddish iron ochry-looking substance occurs disseminated through 

 this variety; 6th, a very compact primitive limestone, with a texture 

 approaching to that of calcareous spar ; 7th, a limestone, or marble of a 

 whitish color, consisting of a congeries of minute grains, which appear to 

 the naked eye rounded, but which seen through a microscope have an imper- 

 fect crystalline structure, exhibiting sharp angles, &c. — through this rock 

 is disseminated minute scales of a dark colored mica ; 8th, a limestone 

 somewhat similar to the last, of a cream-color, composed of similar grains 

 in a very loose state of aggregation, so that it crumbles into a fine calca- 

 reous sand almost on being handled. Through this rock are disseminated 

 scales of an olive-colored mica, and a portion of it being thrown into nitric 

 acid, the calcareous grains were completely dissolved with brisk efferves- 

 cence, while there remained as a residuum, the scales of olive-colored 

 mica, a few minute grains of quartz, and two other minerals, the nature of 

 which I do not altogether understand. 



One occurred in small cylindrical grains, or rather six-sided prisms, the 

 lateral planes of these not being very well marked, but at the same time 

 sufficiently distinct to entitle them to the appellation of crystals. They 

 are about the size of a grain of rice, are slightly translucent, approaching to 

 opaque — of a white color and silky aspect ; they are soft, and easily crum- 

 ble between the fingers into a fine silky looking powder. Before the 

 blow pipe they acquire a more opaque degree of whiteness, and they do 

 not appear to be affected by acids. Their specific gravity does not seem 

 to exceed 2° 00, but from the smallness of the size of these crystals, and 

 from their lightness, I could not ascertain this point with precision, not 

 being possessed of scales sufficiently delicate. 



