MINERALS AND GEOLOGY OF CANADA. 3 
The following are the characters in question : 
. Aspect or Lustre. 
. Colour. 
. Streak. 
. Form. 
Structure. 
. Hardness. 
. Specific Gravity. 
. Relative Malleability. 
. Magnetism. 
. Taste, &c. 
SOS ONATP OD aw 
— 
1. Aspect or Lustre.—We have here to consider, first: the hind ; 
and, secondly, the degree or intensity of the lustre, as possessed by 
the mineral under examination. The kind of lustre may be either 
metallic, as that of a piece of copper, silver, &c.; or sub-metallic, as 
that of most kinds of anthracite coal; or non-metallic, as that of 
stones in general. Of the non-metallic lustre there are several varie- 
ties, as, more especially : the vitreous or glassy lustre—example: rock- 
crystal ; the resinous lustre—ex.: native sulphur; the pearly lustre— 
ex.: talc; the sdlky lustre (usually accompanying a fibrous struc- 
ture)—ex.; fibrous gypsum; the stony aspect; the earthy aspect, 
&c. These terms sufficiently explain themselves. Occasionally, two 
kinds of non-metallic lustre are simultaneously present, as in obsi- 
dian, which exhibits a ‘‘resino-vitreous’’ aspect; and the lustre in 
some zeolites is pearly within, and vitreous externally. In mica, and 
some few other minerals, there is frequently a pseudo-metallic lustre. 
This may be distinguished from the metallic lustre properly so-called, 
by being accompanied by a degree of translucency, or by the powder 
of the mineral being white or light-colored: minerals of a true me- 
tallic aspect being always opaque, and their powder being always 
black or dark-colored. So far as regards the metallic and the non- 
metallic lustres, there are very few minerals which exhibit (in their 
different varieties) more than one kind. Thus, galena, the common 
ore of lead, copper pyrites, &c., always present. a metallic lustre ; 
whilst, on the other hand, quartz, feldspar, cale-spar, gypsum, &c., 
are never found otherwise than with a non-metallic aspect. Hence, 
by means of this easily-recognized character, we may divide all 
minerals into two broad groups; and thus, if we pick up a: specimen 
