96 THE ROYAL SOCIETY OF CANADA 



VEINS CONTAINING ARSENOPYRITE AND GOLD. 



Beaver Lake. Gold has been found rather widely distributed in 

 quartz veins in an area of Pre-Cambrian greenstones and schists on 

 the north side of Beaver Lake in the Province of Saskatchewan, close 

 to one of the principal waterways used by the early fur traders when 

 on their way from Montreal to the Churchill and Athabasca districts. 



The rocks in which the gold-bearing veins occur are acid quartz- 

 mica schists, and altered quartz and feldspar-porphyries, all included 

 in the much disturbed Archaean complex, and probably all of Keewatin 

 age. 



The Mica schists are well exposed on the property of the Beaver 

 Lake Mining Company. The more massive varieties consist of a 

 groundmass of finely granular quaitz mixed with an abundance of 

 biotite, included in which are larger crystals of feldspar, both striated 

 and unstriated. Most of these crystals have been much crushed, and 

 now have ragged edges, their borders being often altered to calcite. 

 The foliation of the schist is distinct and regular, and dips N. 70° W. 

 L 35°. Close to the principal quartz vein on this property the schist 

 is much more thinly foliated than elsewhere, and under the microscope 

 the constituent minerals show a definite linear arrangement. This 

 rock has probably been originally the same as the more massive variety 

 mentioned above, but the minerals in it are as a rule more decomposed, 

 calcite is more largely developed, and narrow bands of secondary 

 quartz are fairly abundant. The schist is also impregnated with 

 small well formed crystals of arsenopyrite. Cutting across the schist 

 are many minute fractures or jointage planes, in which pyrite is often 

 present. 



The veins in which the gold occurs are of white quartz, associated 

 with which are sericite and perhaps chlorite in dark irregular patches 

 and narrow bands. In these darker patches and bands gold may oc- 

 casionally be seen. The veins conform closely in dip and strike with 

 the foliation of the schist. I was able to obtain gold on assay also in 

 the schist impregnated with arsenopyrite adjoining the veins, and I 

 believe the gold has been introduced with the arsenopyrite. 



On the Eagle and Beaver Claims, which lie some distance south 

 of the property of the Beaver Lake Mining Company, the rock is a 

 schistose andesite-porphyry with a pepper and salt appearance on 

 weathered surfaces, varying to a fine-grained chlorite schist. The 

 coarser parts of this rock are composed of phenocrysts of plagioclase 

 imbedded in a groundmass of rod like crystals of plagioclase and flakes 

 of chlorite ? which are drawn out and wrapped closely round the felds- 

 par phenocrysts. The finer grained rock has largely gone to chlorite, 

 but contains much secondary quartz, calcite and arsenopyrite. In 



