OF CENTRAL CANADA PART II. 93 



soda, if the latter be added littfe by little until the proper quantity be 

 obtained ; but phosphor-salt is a far more characteristic reagent for 

 these bodies. When a silicate is exposed in a bead of phosphor-salt 

 to the action of the blowpipe, the bases (lime, magnesia, alumina, 

 &c.) become gradually taken up, whilst the silica remains wholly or 

 in chief part undissolved. A small portion may be taken up by the 

 hot flux, but as this cools, the silica is precipitated, rendering the 

 glass opaline or milky. The undissolved silica, if a small fragment 

 or scale-like particle of the mineral be subjected to the test, forms a 

 thin, translucid, flocculent mass, technically known as a "silica 

 skeleton," in the centre of the bead. A silicate may thus be readily 

 distinguished from a phosphate, carbonate, sulphate, &c., as these 

 latter bodies are rapidly and entirely dissolved (the carbonates with 

 effervesence) by phosphor-salt under the action of the blowpipe. 



The silicous minerals, hitherto discovered in Canada, are described 

 in this work under twelve groups or sub-divisions ; but some of 

 these, it should be observed, are rather groups of convenience than 

 strictly natural collocations. Their distinct characters are given 

 below. The groups, themselves, comprise : (1) Quartz group; (2) 

 Basic Silicates ; (3) Pyroxenic Silicates ; (4 > Chrysolitic Silicates ; 

 (5) Feldspathic Silicates; (6) Calcareo-Feldspathic Silicates; (7) 

 Nephelitic Silicates; (8) Zeolitic Silicates; (9) Micaceous and 

 Chloritic Silicates ; (10) Talcose Silicates; (11) Kaolinic Silicates ; 

 (1'2) Copper and Nickel Silicates. 



(1) QUARTZ GROUP. 



[This group includes the different conditions of Silica in its free or 

 uncombined state. These conditions aje principally three : the 

 crystalline anhydrous condition yielding the different varieties of 

 Quartz ; the Calcedonic condition ; and the uncrystalline, generally 

 hydrated condition, giving rise to the various Opals. 



43. Quartz : Colourless or variously coloured, and vitreous or 

 stony in aspect. Streak (normally) white. Frequently found in 

 Hexagonal crystals, consisting almost invariably of a six-sided prism, 

 transversely striated, and terminated by the planes of a six-sided 

 pyramid. In many examples, however, the pyramidal planes, more 

 especially, are of very unequal size, some of the faces being often 

 abnormally developed so as to produce the partial or complete 

 obliteration of the rest. The point of the pyramid is thus often ex- 



