ARCH/EAN. 



shown in the case of the nepheline syenites of Alno by Hogbom, 1 

 and in that of the elseolite-syenites of Sivamalai by Holland, 2 and 

 it is even known to occur, as a primary constituent, in granite. 3 

 There is one circumstance in connection with the presence of 

 graphite in the Ruby Mines limestone which tends 



Organic origin of ° . . , , , , , 



graphite. to indicate that the carbon may be ot organic 



origin, namely, that this mineral has not been 

 found in the gneisses with which the limestone is intercalated, but is 

 confined to the latter rock. The deposits of graphite near Wabyudaung 

 (Wapudoung, C. B. B.), which have been opened out and worked 

 to a small extent by the Ruby Mines Company, occur along the 

 line of contact between the gneiss and limestone, but it is not 

 disseminated through the gneiss. In Canada, however, where the 

 association of graphite with crystalline limestone and gneiss seems 

 to be very similar to that we are dealing with, the graphite is 

 disseminated through both rocks. But F. Cirkel, in his mono- 

 graph on graphite,* is of opinion that the graphite of limestones 

 is derived from carbon originally present in the rock, probably of 

 organic origin, and on the other hand, following Weinschenk, 5 that 

 the source of the graphite veins in the gneiss must be sought deep 

 in the earth, where it is supposed to have been deposited from 

 carbon monoxide and compounds of the cyanogen group. 



Further light has been thrown upon the question of the origin of the 



crystalline limestones of Upper Burma hy the 

 Crystalline limestones ' . „ , J . 



of Naniazeik. researches of Dr. A. W. Cr. Bleeck, of Munich, 



who has examined the rocks of the Manwe- 

 Naniazeik ruby tract in the Kachin Hills. 6 Describing the limestones, 

 he says : — 



" Every single specimen possesses the peculiarity of giving off an evil 

 smell when struck with the hammer. This smell originates from organic 

 matter, probably skatole." 



This observation would equally well apply to the limestone of 

 the Mogok Ruby Mines, indeed so powerful is the odour that on a 

 hot day it is not necessary to strike the rock with a hammer in 



1 A. G. Hogbom, Nepheline-syenite of Alno ; Oeol. Foren. Stockholm Forhand. 

 XVII, 2 and 3, pp. 100 and 214. Abstract in Mineral Mai/., Vol. -\ I (IS!).")), p. 2f>0. 



2 T. H. Holland, op. cit., Memoirs, Oeol. Surv. Ind., Vol. XXX, Ft. 3, p. 197. 



3 E. Rimann, Ueber calcitf uhrendcn Granit in Riesengebirge, Centralb. jiir. Min. 

 Geol. u. Pal. Jahrg., 1907, p. 203. 



4 Graphite, its Properties, Occurrence, Relining and Uses, Ottawa (1007). 



5 E. Weinschenk, Bildung des Graphites ; Zcitschr. f. Prakt. Geol., 1903, p. Iti. 



6 On Rubios in tho Kachin Hills ; Btcords, Geol. i>uu: Ind., Vol. XXXVI, 1't. 3, p. 104. 



