It is an iron sesquioxide, or ferrous oxide, containing 70 per cent of iron and 30 per cent of oxygen, when pure, but clayey and sandy impurities are sometimes present. Hematite crystallizes in the hexagonal system, although when properly so called, it is granular, reniform, or amorphous, the crystallized variety being specular iron. The common forms of the crystals are rhombohe-drons. Cleavage is parallel to the faces but generally indistinct, and hardness is 5 1/2 to 6 1/2. Specific gravity varies from 4.5 to 5.3, and the refractive indices are 2.94-3.22. Although opaque except in very thin plates, a highly metallic luster is exhibited. Beneath the surface of the reniform variety, or kidney ore, a radiating columnar structure is often visible. A streak of a dull red color when rubbed on a piece of unglazed porcelain or ground glass is a test for this stone. Magnetite would leave a black streak, stibnite a gray, and pyrites a greenish black mark. It is harder than jet, yet softer than onyx, and it is really not suited for use in jewelry. But it is cut, sometimes in intaglio form, and the mounted jewelry can be seen more generally in Spain, France, Mexico, and some southern American countries. Some engraved pieces have been found in old Egyptian graves and in the mines of Babylon. Earthy types of hematite have been used in the manufacture of crayons, for polishing glass, and as a red paint. Its chief commercial importance lies in its richness in iron. The rough stone occurs in rocks of all kinds, and often in pock ets in the surface of carboniferous limestone. In some instances, lodes of several yards in thickness have been found, while two hills in the state of Missouri were once almost entirely composed of massive and micaceous hematite. Material comes from the Alps, France, Norway, Spain, England (North Lancashire, Cumberland, Devon, Cornwall), Wales, U.S.A., India, Elba, Norway, Sweden, U.S.S.R., and also in many volcanic regions. It is, indeed, found in most parts of the world, but much of the new material used in jewelry of late years has been cut in Germany and France from rough found in Cumberland. |
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This stone was once used in mourning jewelry, like jet, but now it is again seen in mounted forms, but mainly in districts where the rough stone is mined, and where it is sold as a "local" stone. In color, hematite is black with an iron, metallic luster, although thin pieces appear by transmitted light to be transparent and tinged a blood red color. This property gives us the name for the mineral, the corresponding Greek word (haema—blood), meaning bloodstone.