2 CHARACTERS OF MINERATS. 
by art, as we term it, is not a product of art, but a result solely 
of the fundamental laws cf 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 sinall part of those which make up 
the inorganic kingdoin or division of Nature. 
OHARACTERS 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. ‘hey are included under piane 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- 
ea] 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 characters 
are embraced in the department of PuystcaAL MINERALOGY. 
Jn addition to the above-mentioned branches of the science 
