64 The American Geologist. jan. i89o 
them, and that it has much better defined characteristics, 
which permit a specific description and entitle it to a distinct- 
ive name. 
Wurtzilite occurs in large, homogeneous masses, free from 
mechanical admixture and without any evidence of formation 
in layers, or of fusion. It is amorj^hous, and when cold, or at 
ordinary temperature, it is brittle and breaks with a large con- 
choidal fracture, giving very brilliant, glossy surfaces with a 
vitreous lustre like uintahite, and resembling in appearance 
the splendent conchoidal surfaces of newly-broken obsidian. 
It has, however, a degree of toughness which increases with an 
elevation of temperature, and it requires a quick, sharp blow 
to detach a flake and secure a good fracture. 
Elasticity is observable in thin flakes, but this elasticity may 
be compared to that of glass or mica rather than to the yielding 
tensile elasticity of "rubber." If the flake is bent too far, or 
suddenly, it snaps like glass. The substance is also flexible 
and when slowly pressed and warmed a flake may be bent 
nearly double. 
Color. — The extremely thin edges of the flakes obtained by 
fracture are garnet red by transmitted light, and are often bril- 
liant. It would thus appear to be transparent in very thin 
plates, and to be deep red in color. The color of the mass by 
reflected light is a jet black. 
Hardness. — The hardness is such that it is not impressed 
by the nail at ordinary temperature. It scratches gypsum, 
and does not scratch rock salt. It is thus between two and 
three in the scale of Mobs. 
Specific Gravity— dX 60 degrees F., 1.030. 
Fusihility. — Does not fuse in boiling water, but becomes 
softer and tougher, and is more plastic, but is not viscid or 
sticky, and fragments are not adherent. It melts in the 
flame of a candle, takes fire, and' burns with a bright, 
luminous flame, with a slight crepitation and little 
smoke, giving off a strong bituminous odor. Fused in a 
glass tube it gives off a dense cloud of white and yellow 
smoke and distils over a thick, brown, tarry oil Avith a strong 
odor, and leaves a small residue of fixed carbon. Fragments 
warmed in the hand emit a strong odor like that of some of 
the crude petroleums, which is rather offensive. 
Electrical Characters. — It is a good electric. Negative 
electricity is easily developed by friction. It will be found 
useful as an insulating material and for other purposes in the 
arts. 
Insolubility. — It is not easily dissolved. It resists the 
usual solvents of bitumen, but experiments are in progress 
which will probably lead to a process by which it can be suc- 
cessfullv worked in combination with other substances." 
