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



have been worked. In the Dominion deposits of wolframite and 

 scheelite seem to be of almost equally common occurrence, but they 

 do not show many features of theoretical interest. The only point 

 needing to be mentioned is that in several instances wolframite has 

 been found in quartz veins with scarcely any other metallic minerals ; 

 occasionally a little pyrite or chalcopyrite is found. In Inverness 

 County, Cape Breton, for example, hiibnerite is found in quartz veins 

 with a little chalcopyrite. In York County, New Brunswick, 

 wolframite occurs in quartz veins with molybdenite, pyrrhotite, 

 arsenopyrite, and a little cassiterite ; topaz and fluorite are found in 

 the gangue ; this is evidently a transitional type. In the Kootenay 

 district of British Columbia wolframite is found in some quantity 

 along with gold in quartz veins cutting granite and various Palaeozoic 

 rocks. Here little or no sulphide ore is to be found. In the 

 Cariboo district wolframite occurs in A'^eins with galena and pyrite, 

 while in the Yukon it is found associated with native gold and 

 bismuth. All these occurrences should be considered in connexion 

 with the gold-tungsten ores of Colorado and Dakota ; the general 

 question of the relations of this type will be discussed later. 



In most of the wolfram mines of Queensland, as before described, 

 the ores are associated with large quantities of tinstone, the latter 

 being in most cases the more valuable of the two, but at Mount 

 Carbine tinstone is so small in amount as to be negligible. This 

 may therefore be regarded as an occurrence belonging to the present 

 section of the subject, although tinstone does occur in quantity in 

 other parts of the same district. The ores occur in pegmatite dykes 

 in connexion with granites intrusive into schists and slates, which 

 are highly metamorphosed and are often intensely silicified. The 

 plans of the workings show a network of interlacing veins, varying 

 in size up to 6 feet wide, but usually about 2 feet. The gangue is 

 variable in composition, sometimes it is wholly quartz, while other 

 veins consist chiefly of felspar ; in the mixed veins quartz usually 

 predominates ; muscovite is rare, while tourmaline and beryl also 

 occur in small quantity. The only other metallic mineral found is 

 a small quantity of molybdenite. Wolframite has been found in 

 very large blocks, one weighing 6 tons, but it is more common in 

 bladed and acicular forms. So far as the genesis of these deposits 

 are concerned, it is quite evident that they Avere derived from 

 a granitic magma, like the tinstone-wolframite ores of other parts of 

 Northern Queensland ; their occasional association with tinstone in 

 the immediate neighbourhood is clear proof of a common origin, and 

 it appears that the portion of the granitic magma which gave rise to 

 the pegmatitic lodes of Mount Carbine itself had undergone a more 

 than usually advanced degree of differentiation, so that the tin- 

 wolfram-bearing fraction had been almost completely separated from 

 the fraction carrying wolfram alone. The mechanism of this 

 separation is uncertain, but it may be connected with differences 

 in the freezing-point of compounds of tin and of tungsten respec- 

 tively with the volatile elements of the magma, possibly the 

 fluorides. From a consideration of the facts observed in other areas, 

 such as Cornwall, it seems probable that tungsten is more volatile 



