MINERALS AND GEOLOGY OF CANADA. 521 
colour, imbedded (usually with accompanying scales of graphite,) in 
crystalline limestone. H 6-6°5; sp. gr. 3:1-3°2.  Infusible, but 
becomes white before the blowpipe. With borax. melts into a clear 
glass, which, if thoroughly saturated, may be rendered milky by 
flaming. This mineral is a silicate of magnesia, combined with a 
small proportion of fluoride of magnesium. It dissolves with gela- 
tinization in hydrochloric acid. Condrodite occurs in some abundance 
in the crystalline limestones of our Laurentian rocks, more especially 
in the townships of South Crosby (Leeds Co.) C. W., and Grenville 
(Argenteuil Co.*) C. E. Also in St Jerome, (Terrebonne Co.) 
in the Lower Province. 
Olivine :—In green, yellow, or brownish grains and granular masses 
(sometimes crystalline) in the eruptive rocks of Montreal, Rouge- 
mont, Montarville, etc., in Eastern Canada, as first recognised by Mr. 
Hunt of the geological survey. H 6:0-6°5; sp. gr.3°3-3°5. Infusible, 
gelatinizes in hydrochloric acid. Composed of silica and magnesia, 
the latter usually in part replaced by protoxide of iron, 
Tourmaline :—(infusible varieties) : yellow, green, etc., mostly in 
tbree or nine-sided prisms. This mineral is described under C 3, the 
Canadian varieties being (chiefly) fusible. 
Feldspar (Including Orthoclase, Albite, etc.,):—In white, red, 
green, or greyish cleavable masses and crystals. Fusible in thin 
splinters. See Section C 3. 
The following minerals may also be referred to, in connection with this group :— 
Opal.—Hydrated silica. A vitreous, or resino-vitreous mineral of various colours, 
occurring only in nodular or amorphous forms. Sp. gr. 2°0-22. Gives off a little 
water in the bulb-tube. The iridescent varieties constitute the noble opal; the 
colourless glassy variety in botryoidal masses, forms the hyalite ; whilst the opaque, 
or faintly translucent varieties, of white, grey, red, brown, and other colours. 
comprise the semt-opal, milk opal, wood-opal, &e. Although this mineral, at least 
in its coarser varieties, is exceedingly common in the old world, (chiefly in 
amygdaloidal cavities in trap and voleanie rocks,) it appears to be of very rare 
occurrence in North America. 
Beryl.—Chiefly in six-sided prisms and columnar masses of a light green colour. 
Fusible with great difficulty, and only on the thinnest edges. H. 7°5-8; sp. gr. 
26-28. Common in many parts of the United States. The clear bluish-green 
varieties are employed in jewellery under the name of Aquamarine. The rich, 
deep green varieties (chiefly from New Grenada) form the well-known Emerald. 
* This is incorrectly printed ‘ Addington Co.’ at page 178, line 5. 
