P52 A POPULAR EXPOSITION OF THE 
The following minerals may also be referred to, in connexion with this group :—= 
Red Copper Ore (sub-oxide of copper.) Red, with red streak; often in octahe- 
drons and rhombic dodecahedrons, converted on the surface into green melachite ; 
fusible and reducible per se, colouring the flame green.—Black Oxide of Copper. 
Chiefly in black, earthy, or amorphous masses, (or cubical crystals) from the south 
shore of Lake Superior. Blowpipe characters like those of red copper ore.—Red 
Zine Ore. In granular or Jamellar masses of a red colour, with orange-yellow 
streak. Lustre inclining to semi-metallic. H.4:0-4°5. Quite infusible. Hitherto 
found only in New Jersey. Normal composition: Oxygen 19°75, zine 80°25; but 
sesquioxide of manganese, to the amount of 3 or 4 per cent., is present, also, in 
most specimens. 
DA. Streak, white. Anhydrous. Not yielding water in the bulb-tube. 
The Canadian minerals of this group may be conveniently arranged in several 
sections, as follows: $1. YieLpine to THE Natt: Mica of different kinds; cer- 
tain varieties of Tale; Asbestus.—§ 2. EFFERVESCING STRONGLY IN COLD Hypro- 
catoric Actp: Calcite or Cale Spar.—§ 3. ErrervescING FEEBLY IN COLD, BUT 
sENSIBLY IN Hor Acrp: Dolomite, Magnesite.—§ 4, Fustste: Fiuor Spar (phos- 
phoresces) ; Heavy Spar (colours flame pale green); Celestine (colours flame red) 
—Inrusiste: Light-coloured varieties of Zine Blende. 
§ 1. Yrnnpine to THE Natt. 
Mica.—The term “mica” includes properly, a series of distinct 
though closely allied silicates, presenting equally a metallic-pearly 
lustre and a strongly-marked foliaceous or fissile structure, the thin, 
component laminz of which are flexible and elastic. These distinet 
species being, however, in many instances, of very difficult separation 
—frequently requiring indeed, for that purpose, the aid of accurate 
chemical analysis, and minute optical and crystallographic investiga- 
tion—they may be grouped together in an Essay like the present, 
more especially with regard to their geological bearings, and treated 
practically as one species. Thus considered, mica occurs in foliated 
and scaly masses, and occasionally in six-sided and rhombic prisms, 
of a white, brown, black, grey, green, red, or yellow colour, with 
pseudo-metallic or pearly aspect. The prisms are 
often tabular, as in figure 46. H. 1:0 on the faces 
or broad surfaces of the lamin, and sometimes as 
high as 5:0 on the edges. Cleavage very strongly 
Fig. 46. marked in one direction, so that by means of the 
finger-nail, or the point of a knife, leaves of extreme tenuity may be 
obtained. These are flexible and elastic. Sp. gr. 2°7—3:1. Some 
varieties are fusible ; others become opaque before the blowpipe, but 
