30 MIPDLEM18S: THE GEOLOGY OF IDAR STATE. 



which ramify and cut across the foliation of the gneiss in a very 

 complicated way. Near the summit, and down the descending spurs, 



Fig. 8, 



occur numerous enclosed blocks of the overlying Delhi Quartzite 

 with contact-minerals as at Dijio. 



Several other little hills east of this, and surrounding a dry tank 

 (reservoir)-bed, are similarly composed, the dip of foliation being 

 east at about 60°, and containing included blocks of the Delhi 

 Quartzite. On the east these exposures are connected in a dis- 

 jointed way with the Delhi Quartzite masses of the main hill-range. 



In the gneiss of the 858 ft. hill, No. £ft (12294, PI. 9, fig. G), the 



quartz, andesine-labradorite and biotite are much 



Microscopic details. ^ ^^ ^ Jr ^ j^ rf)ck; bufc ^ arrange( j 



in smaller and more closely parallel layers. There is, however, in 

 addition, a fair amount of irregularly bounded areas of highly re- 

 fracting, colourless material, which appears to be all diopside. There 

 is also some calcite and minute zircons. No. s 2 7 ° 7 (12295), an 

 included block of quartzite in the biotite-gneiss of the 858 ft. hill, 

 is very similar to the included blocks of Dijio ( 8 %, 12290), the contact- 

 minerals developed being garnet, diopside, wollastonite and gran- 

 ules of sphene, but there is not so much garnet. The undeter- 

 mined pink mineral is also visible in the hand-specimen. 



The next and last outcrop of the biotite-gneiss of these eastern 

 exposures is in the low 93G ft. group of hills, 



Outcrops near U.dl,. ^^ q{ ^^ They ^ cornp l et ely isolated 



by alluvium from all other rocks, but on the west the calc-gneiss 

 is not far away. Here, as before, the dip of foliation is easterly at 

 about 40° and the gneiss is penetrated by aplite veins, so that the 

 whole exposure is suggestive of a non-calcareous variant of the 



