12 



IIAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



reveals the presence of a number of compressed anticlines, and the whole 

 series has evidently been repeatedly folded (fig. 3). Even in the 



1, Crystalline limestone ; 2, Schist. 

 Fig. 3. 



Folded crystalline rocks of the Ruby mines. 



individual beds of crystalline limestone the dip is very capricious, and a 

 band, which was dipping to the south at one point, was found at a few 

 hundred yards further along the strike to be dipping to the north. 



The crystalline limestone is quite the most interesting of the rocks 

 of the Siah Koh, and bears a close resemblance to the similar miner- 

 alised limestones of India and Burma. The number and variety of the 

 accessory minerals is not perhaps so large as in the limestones of Mogok 

 and Sagyin, nor is the size of the individual crystals of these minerals 

 so great, but otherwise the two are very much alike. The commonest 

 minerals in the Jagdallak marble are phlogopite, graphite, chondrodite, 

 spinel and garnet ; here and there also pyrite, muscovite and corundum 

 in the form of ruby or, rarely, sapphire. A marked point of difference, 

 however, is the almost complete absence of pyroxene-gneiss, pyroxene- 

 granulite and khondalite (quartz-garnet-graphite-sillimanite schist) . 

 Only one cf these rocks has been observed and that in quite insigni- 

 ficant quantity. In one locality, at about 4 miles to the east of Jagdal- 

 lak, of small band of pyroxene-granulite was observed in the crystalline 

 limestone. The beds are vertical and the limestone contains hornblende 

 biotite schist and biotite-granite in thin parallel bands The granite is 

 of the augen gneiss type but is clearly intrusive ; the schist may be 

 due to the metamorphism of arenaceous bands inteibedded with the 



