MINERALOGY. 185 



bodies. Six different kinds are enumerated by Werner, distin- 

 guished according to their relative length, breadth, and thick- 

 ness, their relative magnitude, and their connections with other 

 minerals. These are, massive disseminated in angular pieces 

 in grains in plates and in flakes or thin laminae. 



Particular external shapes differ from the others in bearing 

 a resemblance to natural or artificial bodies. These are elongat- 

 ed rounded flattened and cavernous. 



Distinct concretions are those parts into which minerals are 

 naturally divided, and which can be separated from one another 

 without breaking through the solid or fresh part of the mineral. 



The external surface of minerals is uneven, granulated, rough, 

 smooth, streaked, or drusy. The lustre is splendent, shining, 

 glistening, glimmering, or dull. And the fracture^ or surfaces 

 produced on breaking mineral substances, is characterized as 

 splintery, even, conch oidal, uneven, earthy, hackly, or slaty. 



The transparency of minerals affords an obvious mark of dis- 

 tinction ; and where it occurs in the highest degree, it is said to be 

 transparent, next semitransparent translucent translucent 

 on the edges, or opaque. The streak is the appearance which 

 minerals exhibit when scratched or rubbed with a hard body, as 

 a knife. In some instances the colour of the mineral is chang- 

 ed ; in others the lustre. The term soiling is used when a mi- 

 neral leaves part of its substance on the fingers ; and tenacity 

 expresses the relative cohesion of the different particles. Besides 

 these obvious characters used in the distinction of species, are 

 frangibility flexibility adhesion to the tongue unctuosity 

 taste and smell. 



By means of these characters alone the different species of 

 minerals may be discovered and arranged. 



Simple minerals are arranged by Professor Jameson into three 

 classes, viz. 



CLASS I. 



Specific gravity under 3.8. If solid, is sapid. No bituminous 

 smell. 



ORDER I. GAS.. 



Sp. gr. = 0.0001, .0.00014. Elastic. Not acid. 



Gen. 1. Hydrogen gas. 2. Atmospheric air. 



