128 



]'i/n>i>hi.'I!ltr — Very plentiful in aggregated, fibrous, radiating 

 masses. 



Prosopite— On the western side of the surface workings this 

 substance is in great profusion. It usually forms a 

 kaolin-like friable mass, throughout which are 

 commonly scattered minute crystals of cassiterite. 



Quartz— Of common occurrence in extensive masses and 

 irregular bunches of interlaced crystals. 



Siderite — In opaque, interbedded, obtuse rhombohedra of 

 large size, of a yellow-brown colour. 



Sphalerite — Of rare occurrence, in small patches with pyrites 

 and the last. 



SHlphnosiderite — This is occasionally met with in the form of 

 thin varnish-like incrustations of extreme thinness 

 of an intense black colour. 



Sulphur — A somewhat large pocket was met with in the 

 Brown Face, intermixed with bunches of minute 

 quartz crystals and prosopite. 



Topaz — This has only been detected of microscopic size as 

 described. 



Tourmaline — This is invariably of the peculiar dark green 

 colour, characteristic of Bischoff. It is usually in 

 felted masses of minute crystals, which rarely 

 exceed 18 millimetres in length. 



Vivianite — Has been obtained in groups of crystals in small 

 fissures in the rock in one of the adits, and also in 

 amorphous, clay-like masses. 



Wolframite — In the West Bischoff this frequently occurs, 

 intermixed with apatite and quartz. 



EXPLANATION OF PLATE. 



Fig. 1. Topaz rock of Queeu Lode, Mount Bischoff x 18. The columnar 

 form of topaz (pycnite) in radiating groups is shown with 

 insterstitial quartz, differentiated under crossed nicols. 



Fig. 2. Topaz quartz-porphyry, Mount Bischoff x 18, crossed nicols. 

 The rectangular section of a large felspar crystal occupies the 

 midd'e of the field. The substance of the felspar has been re- 

 placed by columnar and prismatic topaz. 



