<)0 • /. A. Dunn 



taken. Bromoform being now unobtainable, methylene iodide, 

 diluted to S.G. 3.133 was used for the purpose. This would also 

 eliminate the large amount of muscovite which the rock sections 

 had shown to be present. The final concentrates obtained were 

 weighed : — 



.0658 grams heavy minerals through 100-mesh. 



.0091 grams heavy minerals between 80 and 100-mesh. 



.0749 grams heavy minerals total. 



Heavy minerals in sandstone — .0023 per cetil". 



The heavy minerals were then examined under the microscope 

 :in media of different refractive indices, the following minerals 

 being detected : Zircon, tourmaline, ilmenite, rutile, topaz, sphene, 

 magnetite, spinel, apatite, biotite, corundum, pyrrhotite, arseno- 

 pyrite, chalcopyrite, pyrite, gold; some quartz, chlorite, and mus- 

 •covite, probably brought down with other minerals during flota- 

 tion ; and perhaps monazite. 



Zircon is, with tourmaline, the most abundant. The crystals 

 .almost always show perfect prismatic and pyramidal faces, and 

 in many cases are zoned. 



Tourmaline occurs abundantly as both the brown and bluish 

 varieties, generally in irregular grains, although a crystal face 

 can be occasionally detected. 



Ilmenite is generally altered to white leucoxene, showing in 

 many cases a black, unaltered core. 



Rutile occurs in well-formed prisms, sometimes dark brown in 

 •colour, sometimes violet tinted. 



Topaz occurs generally in irregular grains, but occasionally 

 shows prismatic outlines. The colours vary from colourless, 

 through straw yellow to light greenish yellow. 



Sphene is present in angular and rounded brown grains, gener- 

 allv not so clear as zircon and rutile. The determination is rather 

 ■doubtful. 



Pleonaste, an almost opaque form of spinel, was represented by 

 two or three octahedra. Practically black, but greenish tint de- 

 tected on edges. 



Apatite showing rounded boundaries, owing to the leaching in 

 HCl occurs in colorless and pale-bluish grains. 



Corundum, or sapphire, occurs, but only three irregular grains 

 noted, deep bltie in colour, and rather pleochroic. 



