R. H. Rastall — The Genesis of Tungsten Ores. 199 



as of tia-ore, especially Perak unci Selangor. The mining in these 

 States, as in Burma, is very largely alluvial, but the minerals are 

 also worked in situ in the granites. The tungsten occurrences have 

 been well described by Mr. Scrivenor.' The prevailing rock is 

 a biotite-hornblende granite, locally rich in tourmaline and cassiterite. 

 The other minerals associated in the lodes are arsenopyrite, chalco- 

 pyrite, fluorspar, and topaz, with occasionally sapphire and thorium- 

 cerium minerals. In Selangor the richest shoots of wolfram ore are 

 generally found at the contact of granite and schist ; where the lodes 

 traverse the schists they contain fairly pure wolfram, on the contact 

 they contain mixed ore, while within the granite they become richer 

 in tin and poorer in wolfram. In this area scheelite deposits are also 

 abundant, as will be described in a later section ; the scheelite appears 

 to be genetically connected with the wolfram lodes, and is probably 

 derived also from the granitic magma under somewhat differing 

 conditions. 



The Seward Peninsula of Alaska affords an interesting example 

 of a highly mineralized region of the type now being considered. - 

 The country rock consists of quartzite, slate, and especially limestone 

 of Palaeozoic age, probably Carboniferous. These sediments are 

 intruded by granite bosses and by quartz-porphyry dykes ; the 

 metamorphism thus produced is very intense, especially in the lime- 

 stones, which contain many newly-formed minerals rich in boron and 

 fluorine, such as tourmaline, axinite, danburite, vesuvianite containing 

 boron, and other peculiar tj'pes. 



Wolframite occurs in association with cassiterite in two different 

 ways. On Cassiterite Creek the quartz-porphyry dykes intruded 

 into the limestone are tin-bearing in depth. The tin-ore and 

 wolframite occur as veins and stringers in the dykes, associated with 

 arsenopyrite and pyrite. Blende and galena are less common, Avhile 

 molybdenite is local. The gangiie minerals, besides quartz, are 

 fluorite, topaz, and zinnwaldite. There are also cassiterite-wolfram 

 lodes in the limestone; these lodes appear to be ^egmatitic in origin, 

 as they contain quartz, felspar and mica, fluorite and topaz ; the 

 other metallic minerals are chalcopyrite, pyrrhotite, blende, and 

 galena. 



Another remarkable occurrence is a wolframite-topaz lode, with 

 galena and stannite, on Lost River. The gangue consists of purple 

 fluorite and radial topaz. The presence of some silver is shown 

 by assays. 



From the chemical point of view the most striking feature of this 

 region is the abundance of boron, which has led to the formation of 

 many minerals containing that element, of which the most interesting 

 are paigeite and hulsite, two new iron-magnesia-tin-boron minerals. 

 In this region boron seems to be in excess of fluorine, an unusual 

 occurrence. 



The wolframite output of Queensland comes from the northern 



^ Paper on Tungsten Ores, read before the F.M.S. Chamber of Mines at 

 Ipoh, March 25, 1916 (no place of publication or date). 



" "The Geology of the Seward Peninsula Tin Deposits," by A. Knopf, 

 Bull. 3.58, U.S. Geol. Surv., 1908. 



