ARAVALLI SYSTEM. 39 



gneiss. It is a particularly coarse variety with dark green pyroxene, 

 diopside, especially well preserved ( ( ' A ^ = over 31°). This 

 pyroxene in the hand-specimen is of a dark greenish-grey, with 

 submetallic lustre on the cleavage surfaces. Tn thin section this 

 appears as a pale greyish-green, the central parts being sometimes 

 a more pinkish- and greenish-grey mixed. The central parts can also 

 be seen to be more finely cleaved along the length of the section 

 which gives parallel extinction, being near ^ and at right angles 

 to the clinopinacoid (010). The rock contains some large porphyritic 

 microclines (not seen in the microscope slide, but easily determined 

 in the hand-specimen by cleavage flakes), a fair amount of quart* 

 and some lime-soda plagioclase, which has mostly been converted 

 into scapolite (probably meionite) which is prominently visible in 

 one slide of this rock. There is also some calcite and zoisite- 

 epidote (in one slide). 



This rather peculiar, coarse-grained aplite is not improbably 

 a rock which at contact with the calc-gneiss, into which it is 

 intruded, has itself suffered some contact change or hybridism. 

 Except where the large masses of microcline occupy the rock, the 

 rest of the finer-grained material has quite a large percentage of 

 quartz in it. There is no iron ore. 



Diorite Aplite. 



Specimen no. 4 2 </' 2 (12329, PI. 10, fig. 5 and fig. 6 nicols crossed), 

 from Proia, N.E. of Khed Brahma, forms a prominent cliff in the 

 stream-bed and is intrusive in the calc-gneiss. It is a rather coarse- 

 grained, grey and green speckled rock with a small or moderate 

 amount of quartz. There is no microcline and the presence of 

 orthoclase is doubtful. There is much plagioclase in long lath- 

 shaped sections (albite-oligoclase and (?) also andesine) with albite, 

 pericline, and also Carlsbad, twinning. Diopside, changing to uralitic 

 hornblende, is characteristic and there is much sphene with accessory 

 apatite. Besides the diopside and slight marginal uralite there is 

 also a further border of zoisite, passing into epidote, lying outside 

 the hornblende and coming next the felspar, as was noticed in the 

 calc-gneiss of the same locality ( 3 2 8 ; \) and also in the Khed Brahma 

 vein rock (see sp. 3 2 8 9 2 , 12325). In these cases it seems suggested 

 that the zoisite is a contact effect on the felspars of the uralitisa- 

 Uon of the diopside. 



