14 COLOBADO FERBERITE AND THE WOLFRAMITE SERIES. 



In 1907 a lot of wolframite ore, weighing 1.1 long tons, from Kavens- 

 thorpe, Western Australia, carried 66.2 per cent WO 3 and yielded 5.3 

 ounces of gold. 1 



Examples might be multiplied but would add little weight. The im- 

 portance of those given lies in their bearing on the genesis of tungsten, 

 gold, and silver ores. In many places tungsten ores are closely con- 

 nected with pegmatites or lie in the pegmatites themselves and are 

 probably in nearly all places close to a magmatic source. The gold 

 and silver found in the deposits must be likewise near their place of 

 origin. Of course, it is not to be argued that the absence of tungsten 

 minerals implies that the gold and silver may not be near a magmatic 

 source, but gold and silver appear to accompany siliceous solutions 

 much farther from their igneous source than do tungsten minerals. 

 It seems probable that the tungsten minerals may be deposited from 

 the hotter waters emanating from magmas, and silver and gold from 

 the solutions after they have somewhat cooled. 



. In sections cut for microscopic study from a speci- 



men obtained at the Eagle Rock mine many small, very light green 

 fragments of a uniaxial, optically positive mineral were found. As 

 determined by E. S. Larsen, its indexes of refraction are oj=1.620 

 0.003, e = 1.630 0.003. Its birefringence is 0.010, but some basal 

 sections show anomalous birefringence as though divided into seg- 

 ments. It has a perfect basal cleavage and shows a slight zonal 

 growth. The particles show a tendency toward square sections, and 

 the optical properties suggest that the mineral belongs to the alunite- 

 hinsdalite series. Although very small, the particles are numerous, 

 forming perhaps 10 to 25 per cent of the bulk of this particular ore. 

 (See PL VI.) The gangue is "horny" quartz through which are dis- 

 tributed particles of ferberite and certain other particles which are 

 attracted by a magnet, probably magnetite, both of which occur in 

 grains almost as small as the unknown mineral. An attempt was made 

 to separate the mineral from its gangue by grinding it very fine and 

 passing the powder through a Thoulet solution of 2.8 specific gravity, 

 but the material was too much mixed with quartz to show sufficient 

 improvement for analytical purposes. The fact that with the at- 

 tached quartz it sank through the liquid indicates that its specific 

 gravity is above 2.8, but it is probably not over 3. A partial analysis 

 by George Steiger, in the chemical laboratory of the United States 

 Geological Survey, showed the presence of aluminum, 2 per cent 

 strontium, a very little sulphur as a sulphate, and 3.6 per cent phos- 

 phorus pentoxide. The only heavy metals found were tungsten, 

 iron, manganese, and a trace of titanium. Fluorine and chlorine 

 were absent. There was only a questionable trace of calcium and a 

 very small quantity of magnesium. 



1 Simpson, E. S., and Gibson, C. G., The distribution and occurrence of the baser metals in Western 

 Australia: Western Australia Geol. Survey Bull. 30, pp. 115-117, 1907. 



