--It occurs in great abundance in nature. It is found in
several places in America in the metallic state, and it likewise
occurs in the same state in meteors. It occurs chiefly as the oxide
(red hematite, brown hematite, magnetic oxide, etc.), and frequently
in combination with sulphur. Iron also forms a constituent of the
blood.

Metallic iron is of a grey color, and presents the metallic lustre
vividly when polished. It is very ductile, malleable, and tenacious.
It is very hard at common temperatures, but soft and yielding at a red
heat.

In dry and cold air, iron does not oxidize, but when the air is dry
and moist, it oxidizes rapidly. This likewise takes place with great
rapidity when the metal is heated to redness. When submitted to a
white heat iron burns with brilliant scintillations.

_Protoxide of Iron_ (FeO).--This oxide does not occur pure in nature,
but in union with the peroxide of iron and other substances. It
presents the form of a black powder, and has some metallic lustre, is
brittle, and fuses at a high temperature to a vitreous looking mass.
It is attracted by the magnet, and of course is susceptible of
becoming magnetic itself. It forms with water a hydrate, but this
passes so rapidly into a state of higher oxidation, that it is
difficult to keep it in the pure state.

_Magnetic Oxide of Iron_ (FeO + Fe^{2}O^{3}).--This peculiar oxide is
of a dark color, and is magnetic, so that tacks or small nails adhere
to it when brought in contact with it. It is the variety of the oxide
termed "loadstone." It is found frequently crystallized in octahedrons
in Scandinavia and other places. Magnetic oxide of iron is produced
when red-hot iron is hammered.

_Sesquioxide of Iron_ (Fe^{2}O^{3}).--This oxide is found native in
great abundance as red hematite and specular iron, crystallized in the
rhombic form. In the crystalline state it is of a blackish-grey color,
and possessed of the metallic lustre. When powdered, it forms a
brownish-red mass. When artificially prepared, it presents the
appearance of a blood-red powder. It is not magnetic, and has less
affinity for acids than the protoxide. Its hydrate is found native as
brown hematite.

By exposing the peroxide of iron to the oxidation flame, it is not
acted upon, but in the reduction flame it becomes reduced to the
magnetic oxide.

The oxides of iron are dissolved by borax in the oxidation flame to a
clear dark-yellow or dark-red bead, which appears li