CHAPTER III.
CHEMICAL PROPERTIES OF MINERALS.
The consideration
of the chemical nature of minerals,— that is, of the elements that
enter into their composition,— of the manner in which these elements
combine, and the variations in proportion which they may undergo
without destroying the.identity of the species, forms an important
branch of mineralogical science. The methods of detecting the
different elements, and the characters which are thus furnished for the
discrimination of minerals, are also of much value. This is especially
true of the metallic ores and other substances, sought not as objects
of curiosity, but for their economic qualities.
Composition of Minerals.
At present about sixty elements, or substances which have not been decomposed, are known. These are divided into metallic and non-metallic, a
distinction of importance in mineralogy, though not always to be
carried out with precision. The non-metallic elements are rarely of
semi-metallic aspect, and are bad conductors of heat and electricity.
Some are commonly gaseous—oxygen, hydrogen, nitrogen, chlorine, and
fluorine ; one fluid—bromine; the others solid—carbon, phosphorus,
sulphur, boron, selenium, and iodine. The metallic elements are, except
mercury, solid at usual temperatures, have generally a metallic aspect,
and are good conductors of heat and electricity. They are divided into light and heavy metals, the iormer with a
