& CHARACTERS OP MINERALS. 



by art, as we term it, is not a product of art, but a result solely 

 of the fundamental laws of composition which are at the basis 

 of all material existence; and the chemist only supplies the 

 favorable conditions for the action of those laws. Mineral 

 species, are then, but a very small part of those which make up 

 the inorganic kingdom or division of ^Nature. 



Characters of Minerals. 



1. Minerals, unlike most rocks, have a definite chemical 

 composition. This composition, as determined by chemical 

 analysis, serves to define and distinguish the species, and indi- 

 cates their profoundest relations. Owing to difference in com- 

 position, minerals exhibit great differences when heated, and 

 when subjected to various chemical reagents, and these peculi- 

 arities are a means of determining the kind of mineral under 

 examination in any case. The department of the science treat- 

 ing of the composition of minerals and their chemical reactions 

 is termed Chemical Mineralogy. 



2. Each mineral, with few exceptions, has its definite form, 

 by which, when in good specimens, it may be known, and as 

 truly so as a dog or cat. These forms are cubes, prisms, double 

 pyramids, and the like. They are included under plane sur- 

 faces arranged in symmetrical order, according to mathematical 

 law. These forms, in the mineral kingdom, are called crystals. 

 Besides form there is also, as in living individuals, a distinctive 

 internal structure for each species. The facts of this branch of 

 the science come under the head of Crystallographic Miner- 

 alogy. 



3. Minerals differ in hardness — from the diamond at one end 

 of the scale to soapstone at the other. There is a still lower 

 limit in liquids and gases ; but of the hardness or cohesion in this 

 part of the series the mineralogist has little occasion to take 

 note. 



Minerals differ in specific gravity, and this character, like 

 hardness, is a most important means of distinguishing species. 



Minerals differ in color, transparency ', lustre, and other opti- 

 cal characters. 



A few minerals have taste and odor, and when so these char- 

 acters are noticed in descriptions. 



The facts and principles relating to the above character! 

 are embraced in the department of Physical Mineralogy. 



In addition to the above-mentioned branches of the science 



