90 



MINERALS AND GEOLOGY 



pale-brown or greyish. Tetrag. in crystallization, the crystals often 

 in geniculated twin-combinations. Commonly, also, in columnar am 

 fibrous masses, and sometimes in small grains or scales (imperfect or 

 flattened crystals). H=6.0 -6.5 ; sp. gr. 4.154.3. BB, infu- 

 sible. With borax in a reducing flame, it forms a dark, amethystin< 

 glass, which is transformed into a light-blue opaque enamel by ex- 

 posure to an intermittent flame (see Part I.). Composition : oxygen 

 39, titanium 61. 



Small grains or indistinct crystals of Rutile occur in the beds of 

 Ilmenite at Baie St. Paul, below Quebec ; and at other localities, in 

 Laurentian strata, associated with this ore. Tolerably distim 

 crystals, half-an-inch in length, have been found in crystalline lime- 

 stone on Green Island, Moira Lake, in Madoc.* Acicular crystals 

 occur sparingly in quartz cavities .at the Wallace Mine, Lake Huron. 

 Small crystalline grains and flattened crystals also, in the chloritic 

 schists of some of the Eastern Townships, more especially in Sutton . 

 Minute grains of Rutile occur likewise in many of the black ferru- 

 ginous sands described uuder Nos. 31 and 32, above. 



G. ALUMINA AND ALUMINATES. 



[This group includes but two minerals of Canadian occurrence : 

 Corundum and Spinel. The first, by crystallization and atomic 

 constitution, is related to Hematite, amongst the Iron Ores, and the 

 second to Magnetite\. 



41. Corundum: Blue, blueish-white, red, brownish, greenish, 

 dark-grey ; streak, white or greyish ; aspect vitreous or stony. 

 Hexagonal in crystallization, but occurring 

 frequently in grains and small granular 

 masses. H = 9.0 ; sp. gr. 3.9 - 4.2. BB, in- 

 fusible. Not dissolved by carb. soda. Con 

 sists, normally, of alumina. Transparent blue 

 FIG. 47. FIG. 48. varieties from the Sapphire of commerce, and 



red varieties, the Ruby. Coarse, dull-coloured varieties are known 

 as Common Corundum or Adamantme Spar ; and opaque, dark-grey, 

 granular varieties (often mixed with magnetic iron ore) constitute 

 Emery, a substance largely used as a polishing material. Some of 

 the finer varieties of corundum exhibit, especially when cut, a 

 peculiar opalescence, frequently in the shape of a six -rayed star. 

 These are known as asteria sapphires, rubies, <fcc. 



* This locality was first pointed out by the late T. C. Wallbridge, of Belleville. 



