TAWNG-PENG SYSTEM : CHAUNG-MAGYI SERIES. 



47 



foliation planes, and a little plagioclase felspar : minute crystals of 

 apatite and some schorl (?) are present as accessory constituents. 



The mica schists are everywhere traversed by veins of milk- 

 Q n&rt . white quartz, of all dimensions up to a 



width of several feet, ramifying in all direc- 

 tions through the country rock. These veins are perhaps more 

 numerous near the junction of the schists with the granite, but 

 they are not confined to any particular zone, and on the spurs 

 of the hills they frequently form the only visible outcrops, gene- 

 rally standing out as prominent knolls on the ridges. 



Along the boundary between the gneisses and mica schists 

 Intrusi r 't several strong dykes of intrusive granite 

 ° ' occur. They are well seen on the cart road 

 from Mogok to Mong Long between the villages of Yaunggwin (Ny- 

 aunggon) and Legyi (Lauzee, C.B.B.), and extend for many miles 

 to the east and west of the road. The rock is a coarsely crystal- 

 line granite, consisting mainly of orthoclase felspar with some 

 interstitial quartz and a good deal of tourmaline. Fibrolite, apa- 

 tite and garnet are present as accessory constituents. Extensive 

 excavations for tourmaline (rubellite) have been made in the rain- 

 vash derived from these granites covering the lower slopes of the 

 hills in the neighbourhood of Na-yuk (Nyaungdauk, Nyoungouk, 

 C.B.B.), about 11 miles to the south-east of Mogok. 1 



Chaung-Magyi Series. 



It has been stated above that the boundary between the mica 

 schists and the Chaung-Magyi series is some- 

 Lithological charac- what indefinit and tnat t h e re is reason 

 ters. ' 



for supposing that there is a passage from 



the more highly foliated type of rock to one which shows little 

 or even no signs of alteration. As we proceed southwards from 

 the Nam-pai valley towards the Shan plateau, the well foliated 

 mica schists give place to a series of quartzites, generally of a 

 red or brown colour, occasionally containing a little felspar, when 

 they may be called greywackes, slaty shales, generally dark blue 

 or black in colour, and sandstones. No conglomerates whatever 

 have been observed throughout the whole series, and there are no 

 signs of any stratigraphical break. All the beds are either sandy 



1 C. Bairington Brown and J. W. Judd, Phil, Trans. Roy. Soc„ Voj. 167 A, (1897), 

 p. 185. 



