Mineral Guide > Ores > Iron Ores

Iron Ores

Iron OresThe sulphide of iron, Pyrite, occurs in many crystalline rocks, but, owing to the difficulty of separating the iron and sulphur, is not used as an ore of iron. The mineral much resembles in external appearance a yellow ore of copper, called chalcopyrite, from which it may be distinguished in that it will strike fire with steel.

The black oxide of iron, Magnetite, occurs widely distributed. As its name indicates, it sometimes displays the properties of a magnet.
In a series of ore beds formerly operated by a mining company of northern New York four distinctions of the crude ore were made, two varieties of blue, one of black, and one of gray. The blue coloring is apparently due to the presence of impurities, the black ore is evidently magnetite, and the steel gray mineral, failing in the characteristic properties of magnetite, finds its class place under Hematite. Hematite differs from magnetite in representing a higher degree of oxidation. It is often found, as indicated above, in beds distributed in close conjunction with those of magnetite. This ore is a valuable source of iron. Hematite commonly occurs in earthy materials, as red ochre. Its streak is red. All rocks of a reddish or red color owe the color to this oxide of iron.

When hematite rusts, the brownish-yellow or yellow iron oxide, Limonite, results. The streak of limonite is yellow, thus distinguishing it from hematite. Disseminated through beds of clay, limonite gives them the characteristic yellow color. Such clays turn red when heated, since the water of the limonite is driven off, leaving hematite as a residue. This is the explanation of the usual coloring of bricks. Yellow ochre is impure, or earthy, limonite.

Needle Iron Ore picture