ARAVALLI SYSTEM. 33 



that of a network of veins, frequently from a few inches to a few 

 feet wide, ramifying among, and generally parallel to, the banding 

 or bedding of the invaded series. They are very generallv dis- 

 continuous when any one is followed along its outcrop very far, and 

 not infrequently they appear at the surface merely as eve-shaped 

 sections, 1 to 2 feet long. Hence the individual veins cannot be 

 mapped, except diagrammatically. The rough parallelism of the 

 veins certainly appears as if the result of injection along lines of 

 least resistance, and there is evidence of vague banding or streaki- 

 ness among the minerals of the veins, but not amounting to or 

 resembling in any way the foliation of a real gneiss. Chiefly on 

 these grounds, one is inclined to regard the period of inception of 

 these veins as approximately coinciding with that of the folding 

 and, doubtless, dislocation of the calc-gnciss. Here as in other 

 countries, pegmatite appears to be " the universal healer of all 

 wounds and dislocations in the various rocks of the area " (Adams 

 and Barlow, loc. cit. p. 141). 



The examples in the low hills 1 mile S.S.E. of Khed Brahma 

 are very characteristic. The width of the 



Other characteristics „, „„„ „ \ ± i *. • 1 . 1 



of the veins. exposure here taken at right angles to the 



strike of foliation of the calc-gneiss and also 

 to that of the general run of the aplite veins is about \ mile and 

 within this width there are numerous very small veins from a few 

 inches to a foot across, and as many as 8 or 12 larger veins, 3 to 5 

 feet across. The veins as already remarked, show no foliation, 

 but a rough streakiness parallel to the walls of the veins. Being 

 white in colour and weathering white, they stand out boldly against 

 the darkly weathering calc-gneiss. In the railway cutting 1^ mile 

 S.S.W. of Khed Brahma the fresh surfaces of rock show veinlets, 

 even smaller than a few inches across, and which in some cases 

 seem to merge into the material of the calc-gneiss, though this 

 is probably deceptive, not being borne out by ordinary sections 

 in which the distinctiveness of the two rocks seems fairly established. 

 The material of the veins differs in the relative amounts of the 

 ... , n white and dark minerals and in the class 



Mineral Composition. 



of felspar present, as well as in the amount of 



quartz and the nature of the prevailing dark minerals. These 



latter are characteristically scanty, as in typical aplites, and the 



few patches that do appear are very vague and blurred to the eye, 



even in the freshest specimens obtainable— as if the ierro -magne- 



