12G 



MTDDLEMISS : THE GEOLOGY OF IDAR STATE. 



veins of the pinite with quartz appear in the granite running N. E.— 

 S. W. The pinite is very soft, loses colour before the blowpipe and 

 is doubtfully fusible. It has the optical characteristics of muscovite 

 and also the cleavage. The pale lemon-yellow colour makes the 

 rock very visible on the hill side and foot-hills of the Dharol mass 

 (Specimen Xos. fft — m)* 



QUARTZ-PORPHYRY. 



More or less associated with, but also iu a slightly distinctive 



grouping to, the bosses of Idar granite, come 



General appearance. ^ ^ yery dissimi i ar roc k y tors iim { rilt n, e d 



masses of quartz-porphyry (see PL 7, fig. 2). As a whole this 

 hypabyssal rock is distinctly differentiated from the ldar granite, 

 although local passages through micro-granite seem to be established, 

 as in the tor If miles S.W. of lamia (specimen No. ^-12465), 

 In large masses it weathers a characteristic dark colour, which 

 renders it easily recognisable even at a distance ; whilst in the 

 hand-specimen the same dark-coloured compact ground-mass, some- 

 times almost as compact as a pitchstone, and grains of amethystine 

 quartz, and sometimes pink felspar phenocrysts, distinguish it 

 readily from the neighbouring and associated granite. 



Its cveographical distribution is essentially more local than that 



of the Idar granite, as can be seen from the 



Distribution. m where it is confined to two areas, one 



in a little group of isolated hills between Jamla and Sabli, and the 



other in another mass or group lying south of Mundeti and east 



of Vasai. 



In the former the quartz-porphyry, f 5 \, forms a central area 

 in the middle of the Jamla Delhi Q.uartzite hill-mass, with branching 

 offshoots into the surrounding quartzite. It also builds the isolated 

 little hills of Likhi 4 W and those near Chhapra, Dholpur, Khandiol, 

 and even seven or eight other scattered bosses of various size round 



about Sabli ( 4 Vs)- .,.,,„ •■ 



In the latter (Mundeti) area, it builds the more connected and 

 massive hill containing the 1.167 ft., 1.279 ft. and 1.142 ft. summits, 

 as well as the more detached hummocky little masses due south 

 of Malasa and round about Khalvad. 



There are a very few other isolated occurrences of the quartz- 

 porphyry as at 1} miles due south of Mau. 



