388 On Metallic Minerals. 



perpendicular scarp about one hundred feet from the river, 

 and the same number of feet above its level. The talc, in 

 the talcose schist, is of that variety called silver talc, and 

 its lustre is so strongly that of silver, as to be easily mistaken 

 by the inexperienced for an ore of that metal, (Note 8.) — 

 In this rock veins of larger crystals of talc, of a light green 

 colour, and very pearly lustre occur; they vary from half 

 an inch to one inch in thickness. Other veins about half 

 an inch wide, also occur of a mineral which possesses the 

 following characters. 



MINERALOGICAt CHARACTERS. 



Colour on a fresh fracture, white, which by exposure 

 becomes yellowish. When dry it is slightly translucent on 

 the edges, but being absorbent and hydrophanous, it 

 becomes deeply translucent on the e<lges after exposure 

 to the action of water, in which it softens, becomes brittle, 

 and eventually falls into two or more fragments. Structure, 

 compact; fracture in the small, either even or flatly coii- 

 choidal ; in the large, owing to the interposition of brown 

 mottled scams of a glistening enamel lustre, the fracture 

 is undulated. These seams often exhibit peculiar fibrous 

 markings of a brown colour, occasioned probably by 

 incrustations of rock cork or rock leather ; they render the 

 mineral very frangible in the large ; in the small, when 

 dry, it is not so, but when saturated with water, it is even 

 friable. Its lustre is dull, but it easily acquires the shining 

 polish of enamel. It is scratched by calcareous spar, but 

 not by the nail unless it has been previously soaked in 

 water and is still moist. It has a slight argillaceous odor 

 when breathed on, and is slightly adhesive to the tongue, 

 with the flavor of chalk rather than magnesia.* It has a 



• It has been said tlwt the carbonate of magnesia, ami the pure cai III 



