OF CENTRAL CANADA PART II. 101 



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Fracture, conchoidal. H = 5.5 6.0; sp. gr. 3.1 4.2. BB, 

 intnmesces strongly, and melts into a black and usually magnetic 

 globule. The powder is readily decomposed by hot hydrochloric acid, 

 silica separating in a gelatinous state. General composition ; silica 

 (30 to 38 per cent.), alumina (8 to 17 per cent), iron oxides (8 to 20 

 per cent.), oxide of cerium (usually about 15 or 16 per cent., but in 

 some examples nearly 30 per cent.; generally replaced, however, in 

 part, by oxides of lanthanum, yttrium, &c. ), lime (6 to 12 per cent.), 

 with a small amount of magnesia, and a little water, the latter indi- 

 cating incipient decomposition. Allanite is of comparatively rare 

 occurrence in Canada. Hitherto, only recognized in pitch-black 

 masses or grains in Laurentian strata, as in the upper Laurentian 

 feldspathic rocks around Bay St. Paul and Lake St. John (as first 

 made known by Dr. Sterry Hunt) ; and in the form of a narrow 

 vein in gneissoid strata at Hollow Lake, the head waters of the 

 South Muskoka. (See a notice, by the writer, in Canadian Journal, 

 Vol. IX., p. 103). 



51. Sphene or Titanite : Brown, black, yellow, greenish. Mono- 

 clinic in crystallization (the crystals most commonly, as 

 in Fig. 62) ; but occurring also in small granular masses, 

 and in veins or strings of more or less compact structure. 

 H = 5.6 ; sp. gr. 3.4 3. 6. BB melts with bubbling 

 into a dark glass or enamel, but sometimes on the edges FlG . 62 . 

 only. In powder, decomposed by hot sulphuric acid. Consists of: 

 silica, about 32 per cent., titanic acid, 40, lime 28, but part of the 

 latter is usually replaced by a little oxide of iron and magnanese. 

 Occurs in small dark-brown opaque crystals in the Laurentian 

 gneissoid rocks of Tudor, Madoc, Lutterworth, Muskoka, <fcc. Also 

 in crystalline limestone in Grenville, Burgess, North Elmsley ; and 

 at Lachiiie and Calumet Falls, in the Ottawa country. Sphene is 

 also found in small amber-coloured grains and crystals in the granitic 

 trachytes of the Eastern Townships (Brome, Shefford, Yamaska), 

 and in thin veins or strings with micaceous or slaty iron ore in the 

 altered rocks of Sutton. 



(3.) GROUP OF PYROXENIC SILICATES. 



This group consists essentially of non-aluminous silicates of lime 

 and magnesia, these bases being partly replaced, however, in dark 

 varieties, by protoxide of iron. Alumina is only exceptionally 



