= ‘MINERALS AND GEOLOGY OF CANADA. 525 
general rule, being either infusible, or fusible on the edges only. 
Tourmaline presents a somewhat complex composition, but its 
essential constituents comprise: silica, boracic acid, alumina (or 
alumina and sesqui-oxide of iron) with lime or magnesia, or one 
of the alkalies, or several of these bases combined. Fine examples 
of this mineral vccur in connection with the crystalline limestones 
of the Laurentian rocks at Calumet Island on the Ottawa (greenish- 
yellow crystals); in the township of Fitzroy, Carleton County, C. W-; 
in Clarendon township, Frontenac County, C. W.; in the townships 
of Bathurst and Elmsley, Lanark County C. W.; in Hunterstown, 
Maskinongé County, C. E.; at St. Jerome, Terrebonne County, C. E; 
and other localities. In addition to the general triangular form of 
its crystals and columnar concretions, tourmaline may be distinguished 
from hornblende and other minerals of this section, by exhibiting 
electrical properties when heated. The clear varieties moreover, are 
generally translucent when viewed transversely, and quite opaque 
when viewed longitudinally, even in the shortest fragments. 
Sphene.—This mineral, as regards Canadian localities, occurs in 
small masses or little sharp-edged crystals of an amber- yellow colour 
in the crystalline limestones of the Laurentian series generally ; 
and in the eruptive trap rocks of the eastern Province. H. 5:5; 
sp. gr. 3:4-36, Fusible on the edges with bubbling into a dark 
glass: Essential components: silica, titanic acid, and lime. Our 
best known localities comprise Grand Calumet Island on the 
Ottawa; Burgess township, Lanark County, C. W.; Grenville 
township in Argenteuil County (in crystalline limestone and also in 
trap); St. Jérome parish, in Terrebonne County, C. E.; and the 
eruptive rocks of Mount Johnson, Yamaska, &c., of the district of 
Montreal. 
fpidote.—Chiefly in modified oblique prisms, and in fibrous and 
lamellar masses of a dark or light-green colour, passing into greenish- 
yellow, brown and grey. H. 6:0-7-0; sp. gr. 3:-2-3'5, expands 
before the blowpipe into a slag-like mass, which melts upon its 
edges but resists further fusion. By this latter character it may be 
easily distinguished from hornblende, augite, idocrase, and other 
minerals of this section. Epidote occurs in many of our eruptive 
rocks, as in the greenstones of Lake Superior and the north shore of 
Lake Huron, and in some of the traps of Eastern Canada, although 
