12 MIDDLEMISS : THE GEOLOGY OF IDAR STATE. 



In general terms the calc-gneiss or schist is a roughly equidi- 

 raensional, granular aggregate of fre- 

 Genoral mineral com- fnien tl y large amounts of calcite (when the 

 rock becomes an impure marble, much 

 quarried recently for building purposes on the Khed Brahma ex- 

 tension of the railway). Along with the calcite there occur varying 

 amounts of quartz, felspar (which is generally orthoclase or micro- 

 cline, although plagioclase is also found), diopside (coccolite), 

 occasionally and locally changing to uralitic hornblende, and sphene 

 in relatively large grains. Besides the above, there is locally found 

 a fair amount of biotite, a little graphite and pyrite, and in some 

 few specimens much scapolite, zoisite, wollastonite and minute 

 pale garnet grains. These features of mineral composition suffi- 

 ciently stamp the rock as being in general terms a crystalline granular 

 calc-schist, gneiss or granulite, such as those which in other parts 

 of India are associated with rocks belonging to the Archaean group. 



The area 2 miles north of Vadali and the neighbouring detached 



ridges may conveniently be taken as the chief 



Type areas N. of t yp e f rom w ] 1 f J 1 a selection of specimens will 



now be described. The former restricted area 

 is somewhat irregularly elongated in the direction of the strike, and 

 comprises about 2 square miles of country entirely surrounded 

 by alluvium and rising at its highest point to an elevation of 971 

 feet, or about 200 feet above the general level of the plains at its 

 foot. The main road to Khed Brahma, and likewise the new rail- 

 way, cut through a portion of it. From the. railway and from 

 several quarries on its western scarp abundant rock material is 

 laid bare, as also in many of the hill undulations themselves which 

 are fairly well exposed, especially in the dry, hot season of the 

 year when the long grass has been either burnt or cut for storage. 



From the point of view of the banding of the rock, the western 

 edge of these rolling hills is generally a scarp with dip of foliation 

 about G0° E.S.E., increasing to vertically on the eastern edge 

 of the mass. The N.N.E. — S.S.W. strike veers rapidly at the 

 south-west end of the hill mass so as to carry the outcrops towards 

 the north-north-west in the direction, of the Morad and Dharol 

 exposures. 



The markedly banded appearance of the rock is seen in detail 

 to be due to the layers (| to 4 or 5 inches wide) of more purely 

 oalcite rock, alternating with those in which quartz and felspar 



