Iron oxide. This is a relatively common iron ore. The name comes from the Greek root aima or ema, meaning "blood." because of the red color of the powdered hematite (even the dust of the metallic-looking forml and the color of some larger examples.
Crystal system Trigonal.
Appearance it occurs as thin, relatively brittle, lamellar crystals, polyhedral crystals of lenticuiar habit or mamillated aggregates, all of which are black or dark iron-gray. The lamellae or individual crystals have strong, metallic luster. It may also be incoherent. almost earthy, and red in color.
Physical properties It has a hardness of 6.5 and a density of 5.2-5.3 g/cm“. The very high refractive indices of fie 2.94. nu 3.22 are extremely hard to measure and therefore not of use for identification.
Genesis It is deposited in hydrothermal veins associated with magmatic rocks, although the largest deposits are of sedimentary origin.
Occurrence It is found in large quantities in the United States. Canada, Venezuela. and Brazil, in smaller quanti ties in Italy (Elba). Great Britain. Germany, and Spain.
Reasonably thick crystals (not, therefore, the lamellar ones) and compact, concretionary masses are suitable for cutting into gems and were particularly popular in the recent past.
Appearance Dark, blackish gray, nontransparent and with a metallic luster, hematite is faceted, cut into cabochons, or.engraved; it lends itself. well to the manufacture of signet rings. Other pieces are fashioned into necklace beads or pendants.
Distinctive features The metallic luster and color are highly characteristic; still more so is the red streak it leaves if drawn across a piece of unglazed porcelain.
Occurrence Now used comparatively rarely, the type from Great Britain, Switzerland, Germany, and the island of Elba is suitable for ornamental purposes.
Value Very low. Skillfully engraved items are worth more.
Simulants and synthetics Despite its modest value, it has been imitated by a ferromagnetic, sintered product, moulded to look like engraved stones. It does not appear to have been produced synthetically.