94 



MINERALS AND GEOLOGY 



tended into an edge, as in some of the accompanying figures. Quartz 

 occurs also, and more frequently, in masses of irregular shape, as 

 well as in nodu- 



in 



lar and stalactitic 

 forms, and in small 

 grains. Cleavage, 

 scarcely observ- 

 able: fracture con- 

 choidal and un- 

 even. H = 7.0 ; 

 sp. gr. 2.52.8, 

 mostly about 2.65. FIGS. 51 TO 53. 



BB, per se, quite infusible ; with carb. soda, melts with effervescence 

 (due to the expulsion of the carbonic acid of the flux) into a trans- 

 parent glass. Insoluble in the ordinary mineral acids. Consists, 

 normally, of pure silica, the tints of the coloured varieties being due 

 to accidental amounts of iron and manganese oxides, bituminous 

 matter and other inessential ingredients. The principal varieties of 

 Quartz, hitherto met with in Canada, are as follows : 



( a) Common Quartz, Rock Crystal : Vitreous or stony ; mostly 

 colourless, but sometimes pale reddish, yellowish, greenish or grey. 

 Forms an essential component of granite, mica-schist, gneiss, quartz- 

 rock and various other crystalline rocks, and is thus present through- 

 out the wide area occupied by our Laurentian strata, as well as in 

 many localities where Huronian rocks prevail, and amongst the crys- 

 talline strata of the Eastern Townships (see Part V.). Very common 

 also in mineral veins : as in those of Thunder Bay, Lake Superior ; 

 the Bruce Mines, Lake Huron ; Harvey's Hill Mine, in Leeds ; 

 and elsewhere. Occasionally present likewise, in fissures and cavi- 

 ties in limestone rocks, as in the vicinity of Quebec, where the 

 crystals are known as Quebec diamonds. 



(b) Smoky Quartz : In brownish crystals : Thunder Bay, Lake 

 Superior ; also near Quebec ; and elsewhere. 



(c) Amethyst : In violet-coloured crystals, sometimes of large 

 size. Fine specimens, associated with fluor spar, calcspar, pyrites, 

 native silver, <fec., occur in veins on Thunder Bay and throughout 

 that district ; also on Spar Island, farther west, on Lake Superior. 

 Many of these crystals present a deep reddish-brown colour on the 



