MINERALS AND GEOLOGY OF CANADA. 161 
ming, within the northern geological-basin of Canada. (See Part V. of 
this Essay.) 
Loganite.—This substance named by Mr. Sterry Hunt, in honour of the Director 
of the Geological Survey of Canada, is a very doubtful species. It occurs in sub- 
resinous brownish masses, and in apparently pseudomorphous crystals (after Horne 
blende ? Dana,) in the crystalline limestone of Calumet Island on the Ottawa. H, 
3°0; sp. gr. about 2°6. Composition, according to the analysis of T. Sterry Hunt: 
Silica 32°49, alumina 13°18, sesqui-oxide of iron 2°14, magnesia 35.77, lime 0°95, 
water (and carbonic acid) 16°92. Dana places it under Pyrosclerite, a mineral 
closely related to Chlorite, if, indeed, truly separable from that species, 
Pholerite-—The substance thus named, is usually looked upon as a product of 
alteration, arising from the decomposition of one of the feldspar species, (see Q. 
8, above: Vol. v. p. 528-9,) or, more directly, from the alteration of clay-slate. 
Under this view, it is a kind of Kaolin, with which substance it agrees in general 
composition. It presents, however, peculiar physical characters, much resembling 
those of tale, a mineral with which it is often confounded. Pholerite occurs in 
soft, unctuous, and scaly masses of a pearly aspect, and of a white or pale green- 
ish or yellowish colour, Sp. gr. 2°3—2°6. Before the blowpipe, it exfoliates and 
curls up, but remains infusible. It consists essentially, of silica, alumina, and 
water: the latter varying from 13 to 15 per cent. Nacreous scales of this 
mineral occur, in fissures, in sandstone strata of Silurian age, near the Chaudiére 
Falls in Canada East; and many of the altered slates of the adjoining metamorphic 
region appear to owe their taleose aspect to its presence, or to that of closely 
related non-magnesian silicates of more or less indefinite composition. 
§ 3. YIELDING A LARGE AMOUNT OF WATER. READILY DIs- 
SOLVED BY BORAX BEFORE THE BLOWPIPE: THE BEAD, WHEN 
SATURATED, BECOMING OPAQUE.* 
Gypsum.—(Hydrous Sulphate of lime.)—This important mineral 
occurs chiefly in lamellar, fibrous, and granular masses, of a white, 
grey, yellowish, or other colour, and also in crystals of the Mono- 
clinic System, a common example of which is shown in the 
margin: fig. 50. Lustre often pearly. H=1:5—2:0, (and 
thus, all specimens of gypsum may be scratched by the 
nail,) Sp. gr. 2.25—2°35. Sectile; and, in thin lamelle, 
somewhat flexible. Yields a large quantity ot water in the 
bulb-tube ; becomes opaque in the flame of a candle; and 
Fig. 50. exfoliates and fuses before the blowpipe, into a white enamel, 
Composition : sulphuric acid 46-51, lime 32°56, water 20°93. The 
* The same result is produeed with a moderate amount of the assay substance, when the 
bead is exposed to the action of an intermittent flame: a process technically termed 
“ flaming.” 
