ORDER OF DEPOSITION OF METALLIC VEIN MINERALS. 2 43 



enclosed in siderite, chalcopyrite and ])yrrhotite piercing wolfram, 

 chalcopyrite in pyrrhotite, blende in chalcopyrite and in pyrrhotite, 

 galena and blende on wolfram, flnorite on wolfram, quartz and 

 cassiterite, bismuthinite in fluorite, native bismuth in wolfram, 

 double terminated quartz crystals with one end in cassiterite. Some 

 of these intergrowths are not easily interpreted and mistakes may 

 easily be made if numerous specimens are not available for exami- 

 nation : it is interesting to note that chemical evidence is avail- 

 able which show that lumps of wolfram, with no visible cassiterite 

 may carry estimable quantities of tin. 1 



Dr. W. 11. Jones believes that in general wolfram was deposited 

 at lower temperatures than tin ore. He has stated that the purest 

 wolfram concentrates, that is those which have no cassiterite or 

 only traces of it, are found in veins in sedimentary rocks farthest 

 removed from the granite contact. This fact, to which however 

 there are a few' exceptions, he behoves supports a suggestion made 

 in 1915, that the probable reason why Lower Burma carries more 

 wolfram in proportion to tin-ore than Malaya does, is that the 

 lower part of the Malay Peninsula has suffered greater denudation 

 than Lower Burma and he has added that in Merged, which is 

 between the Tavoyan and the Malayan mines, the proportion of 

 tin-ore to wolfram is greater than in the Tavoy district, and less 

 than in Malaya. It is admitted that there are individual excep- 

 tions, but they are believed to support the temperature zone 

 denudation theory, which has however only to be taken in a broad 

 and general way. If this theory is correct it follows that mining 

 operations in Lower Burma to-day are being conducted in the 

 outcrops and upper horizons of veins which have for the most part 

 been denuded away in Malaya, and that at depth there are in Burma 

 deposits more after the nature of those occurring in .situ in 

 Malaya and which have been the source of its famous tin-fields. 

 Dr. Jones does not suggest that wolfram will in all bases give place 

 below certain depths to tin-ore ; nor that an increasf in depth must 

 necessarily mean a higher temperature zone, but ho believes that 

 the majority of the mines in Tavoy are probably at a zone several 

 hundreds of feet above the part where the temperature was too 

 high for the deposition of wolfram as the predominant ore. 2 



1 W. R. Jones, Mining Mag., Vol. XXU, No. 4, p. 246. 

 *W. R. Jones (15), pp. 41-42. 



