Hematite is a compact form of iron oxide. It varies considerably in compactness and form. Its
hardest and most compact form is the type traditionally used in jewelry as a gemstone. This
is black, and is normally found in massive form as nodules, usually kidney shaped (reniform),
sometimes known as kidney ore.
When crushed or powdered it becomes red, and its less compact forms are also red, streak
tests are also red. The compact black forms have specific gravities and hardness at the higher
end of the range. The softer forms are used as red pigments, and as jeweller's rouge.
Coloration
Gem quality hematite is black, although some describe it as blue-black.
Sources
One of the main sources is Cleator Moor in Cumbria, England, but it is also found in Elba, the
Swiss alps, Germany, Scandinavia, Peru, and the United States. It is often carved or polished
in Idar Oberstein, but much is now processed in places with lower labor costs.
Cutting Styles
Hematite is sometimes used as beads to imitate black pearls. It is also often carved as a
cameo or sealstone, and is very commonly seen in gent's rings with a crude intaglio carving
of a helmeted warrior's head. It is also used as a facetted stone when it resembles black
diamond. Because it is opaque, only the top of the stone is facetted, the bottom of the stone
is typically left flat.
Technical Characteristics
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Chemical Composition:
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Fe2O3 - Iron Oxide
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Hardness:
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5.5 - 6.5
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Specific Gravity:
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4.9 to 5.3
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Refractive Index (R.I.):
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2.94 - 3.22
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Bi-refringence:
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0.28
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Optic Sign:
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Negative
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Optical Character:
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Uniaxial
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Crystal Structure:
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Hexagonal or Trigonal
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