R. H. Rastall — The Genesis of Tungsten Ores. 295 



wolframite. The mineralization is clearly pneumatolytic, as shown 

 by the occurrence of greisen and fluorine-bearing minerals. It is 

 evident that calcium carbonate was abundant in the countrj^ rock and 

 the tungsten compounds of the intrusive magma combined with, the 

 calcium rather than with iron ; that iron was abundantly present is 

 proved by the fact that the iron ores are demonstrably older than the 

 tin ores. This case shows certain affinities with the occurrence at 

 Trumbull, Connecticut, already referred to at some length. The 

 ore-deposits at Pitkaranta are certainly of metamorphic origin, 

 being referable to the intrusion of the Hapakiwi granite, and the 

 metamorphism is equally clearly of pneumatolytic character; the 

 action was selective, and the tungsten-bearing vapours or solutions 

 combined by preference with lime rather than iron. 



As before stated, scheelite occurs in many parts of Canada ; a good 

 example is afforded by the scheelite mine near the Moose lUver gold- 

 mines in Halifax County, JSTova Scotia.^ The country rock consists 

 of highly folded and cleaved quartzites and slates. The veins con- 

 taining the scheelite are similar to the gold-bearing veins in the 

 adjoining gold-mines. They contain quartz, felspar, mica, tourmaline, 

 arsenopyrite, and carbonates (calcite and ankerite). The scheelite is 

 concentrated mainly at the top of anticlines or in the troughs of 

 synclines. These mineralized veins are accompanied by veins of 

 pure quartz of apparently later date. The mineral veins appear to 

 be essentially pegmatitic in their nature, as shown by the presence of 

 felspar and mica. .The non-mineralized quartz veins probably repre- 

 sent a later differentiate from the same source. 



In the Yukon Territory scheelite has been known for some time as 

 a heavy concentrate obtained in gold-washing, and the mineral lias 

 lately been located in lodes in the neighbourhood of Dublin Gulch. 

 It occurs in small quartz veins, Avhich themselves intersect zones of 

 pegmatite within the granite. Wolfram and tinstone also occur in. 

 small quantities. 



At the present time the world's greatest producer of scheelite is 

 California. The Atolia mining district, in the Mohave Desert, on 

 the borders of San Eernardino and Kern Counties, in 1916 shipped 

 1,831 tons of scheelite concentrates, carrying on an average 60 per 

 cent of tungsten trioxide. A large part of this ore is obtained from 

 alluvial deposits, where it is found in lumps up to 100 lb. in weight, 

 but it is also worked to a considerable extent in lodes. These lodes 

 are as a rule more or less continuous fissures in granite, but in some 

 places they appear to be associated with small basic dykes cutting 

 the granite, while in other places the scheelite is found in meta- 

 morphosed limestones at or near the granite contact, associated with 

 garnet, epidote, and other metamorphic minerals. The lodes proper 

 consist of scheelite with a gangue of quartz; they run up to 3 feet 

 in width, and have been followed to a depth, of 700 feet. In other 

 parts of Kern County scheelite occurs in bunches in gold veins, and 

 as nearly pure stringers cutting through slate; also in veins in 

 granite with amphibole, pyroxene, garnet, sphene, and oxidized 



' Eeport of the Geological Survey of Canada, Department of Mines, for the 

 year 1916, Ottawa, 1917, p. 249. 



