198 R. H. Bastall — The Genesis of Tungsten Ores. 



tantalum, niobium, and lithium.^ There are besides a great number 

 of minerals of metamorphic origin, and pneumatolytic action seems 

 here to have been very intense. 



Somewhat similar to the foregoing is the well-known occurrence 

 of cryolite at Ivigtut in Greenland, which also contains cassiterite 

 and w^olframite. The cryolite-bearing mass is about 500 feet long 

 and from 100 to 180 feet wide, lying in granite, granite-porphyry, 

 and gneiss. In the central portion of the mass cryolite predominates, 

 with blende, galena, and chalcopyrite. The marginal portions, which 

 are of pegmatitic character, consist of quartz, felspar, wolframite, 

 cassiterite, molybdenite, and columbite. Fluorite is found in small 

 quantity, but boron minerals are absent.* This mass must be 

 regarded as a special facies of the tin- wolframite pegmatite, 

 characterized by tantalum, niobium, and an enormous excess of 

 fluorine. 



Wolframite deposits occur on a large scale in a zone of country 

 stretching from Tenasserim (Lower Burma) along the western side 

 of the Malay Peninsula through Perak and Selangor. The Tavoy 

 district of Burma and the Federated Malay States are now important 

 producers ; according to the latest statistics available Burma has 

 now the second largest output of any country in the world. 



In the Tavoy district^ numerous granite masses are intruded into 

 the sedimentary rocks of the Mergui Series. These, which are of 

 unknown age, consist of quartzites, quartzitic conglomerates, and 

 schists, the last being often graphitic. The igneous rocks, for the 

 most part biotite granites, contain tourmaline and cassiterite as 

 accessories. The wolfi-am lodes are quartz veins running out -from 

 the granites into the country rock; the chief minerals are quartz and 

 wolframite, which alone occur in any large quantity. The other 

 minerals present are cassiterite, molybdenite, arsenopyrite, chalco- 

 pyrite, bismuthite, galena, and tourmaline. A very characteristic 

 feature is the almost universal occurrence of columbite. According 

 to their mineral composition the lodes can be classified into three 

 groups — 



1. Wolframite-quartz lodes. 



2. Cassiterite-quartz lodes. 



3. Wolframite greisen. 



Of these the first is by far the most important, the second and third 

 groups being apparently rare, but the country is still very im- 

 perfectly explored. 



From a generalization of the published descriptions of the Tavoy 

 area it may be inferred that the mineral assemblage is specially 

 characterized by wolframite, cassiterite, molybdenite, arsenopyrite, 

 and columbite. 



Little is apparently known of the intervening Siamese territory 

 to the south of Tenasserim, although some ore is now exported, but 

 the Federated Malay States are large producers of wolframite as well 



1 Hess, Bull. 380, U.S. Geol. Surv., 1909, p. 149. 



^ Ussing, Danmark Geol. Unters5g., ser. II, No. 12, p. 97; Baldauf, Zeits. 

 fiir prakt. Geol., vol. xviii, p. 432, 1910. 



^ Bleeck, Rec. Geol. Surv. India, vol. xliii, p. 48, 1913. 



