314 McMAHON : PETROLOGICAL NOTES ON SOME PERIDOT1TES, ETC., 



Afghanistan described by me in the Mineralogical Magazine, Vol. IX, 

 p. 187, I have made an analysis of the Shigar rock, which I give 

 below (No. 1) side by side with that of the Afghan bowenite made 

 by Mr. G. T. Prior, M.A., F.G.S., F.C.S., of the Mineralogical Depart- 

 ment of the British Museum :— 



No. I, from Shigar. 





No. II, from Afghanistan 



Silica 



41-13 



44*73 



Magnesia 



43-65 



42-64 



Alumina 



1-23 



0*32 



Iron 



1*49 



o'33 



Lime 



•17 



trace 



Manganese 





••• 



Water 



12*46 



12*21 



Total 



100-13 



IOO23 





__ — — 



_____ 



SpG. 



2-48 



2'59 



H. 



5o 



5'o 



It will be seen from the above that both rocks are substantially 

 the same in composition. In both the hardness is considerably in 

 excess of ordinary serpentine. 



None of the specimens of the Afghan mineral that I have seen 

 have the peculiar sulphur-yellow colour of the Shigar rock. On the 

 contrary they vary from a dark greenish-grey to pale sea-green 

 mottled with white and apple-green. Mr. Lydekker did not see any 

 of the Shigar bowenite in situ. His specimens had fallen from the 

 Mango-Gusor peak and were picked up in the ravines at its foot. 

 All the blocks from this locality appear to have been of yellow colour. 

 Mr. Lydekker saw, however, the apple-green variety at Shigar to 

 which place it is brought in order to be made into cups. He did not 

 see it in situ, but doubtless it is found somewhere in the neighbour- 

 hood. The apple-green variety, Mr. Lydekker states, sometimes 

 shades into yellow or bottle-green. 



1 trust that some future explorer will find the actual outcrop of 



bowenite and ascertain its exact mode of occurrence. Is it in dykes, 



sills or in veins? Does the apple-green variety shade off into the 



sulphur-yellow variety or do they form distinct outcrops? In what 



( 12 ) 



