Properties of Minerals. 87 
therefore, the single mineral should be taken, not a mix- 
ture of mineral, otherwise the analysis would be mis- 
leading. 
_ Where the complete chemical analysis of the min- 
eral species are not given in the tables, those elements 
forming their composition are stated in all cases. 
SECOND PROPERTY. 
LUSTRE. 
The lustre of minerals depends on _ that 
property possessed by some to reflect light from their 
surface. The kinds of lustre are: 
(a) Metallic. The usual lustre of metals. 
(6) Vitreous.—The lustre of broken glass. 
(c) Resinous.—The lustre of the yellow resins. 
(d) Pearly—Like pearl, tale, etc. 
(e) Greasy.—Looking as if smeared with oil. 
(f) Silky.—Like silk, a fibrous structure. 
(g) Adamantine.—The lustre of the diamond. 
(h) Splendent.—Reflecting light with great bril- 
liancy and giving well defined images. 
(i) Shining.—The image produced is not well de- 
fined. 
(j) Dull.—A total absence of lustre, earthy. 
Minerals are transparent when the outlines of ob- 
jects viewed through them are distinct; subtransparent 
when objects are seen but their outlines are indistinct; 
translucent when light is transmitted, but objects are 
not seen; subtranslucent when merely the edges trans- 
mit light faintly, and opaque when no light is trans- 
mitted at all. (J. D. Dana.) 
THIRD AND FOURTH PROPERTIES. 
COLOR AND STREAK. _ 
In distinguishing minerals both the external 
color and the color of a surface that has been 
