The metallic silver-grey crystal surfaces of specular hematite are so highly reflective that they were used in the past as mirrors. It is likely that these reflective qualities and the stone’s brilliant lustre were to blame for hematite’s misnomer Alaska black diamond.
Hematite is a compact form of iron oxide, or rust, and it appears red if cut into thin slices or powdered. Its name derives from the Greek for “blood”. As a gemstone, hematite is opaque and it appears metallic silver to gunmetal grey when polished, and blue-black to dark brown when dull. The material can vary in compactness and form; kidney-shaped nodules and specular crystals are used for gemstones. The lustre of hematite can be dull to submetallic (brilliant).
Types of hematite
The appearance of hematite varies and the stone is marketed under various names. Iridescent hematite is a hematite-rich slate from Arizona that exhibits a multicoloured iridescent surface. The effect is apparently due to long exposure on the mine dumps. Rainbow hematite is a granular specular mass with a high iridescence that occurs in the Minas Gerais area of Brazil. .
Treatments and imitations
- In some countries, hematite is known as bloodstone. It should not be confused with the chalcedony variety of bloodstone.
- Hemalyke is the trade name of a reconstructed material manufactured in the United States. Small pieces of hematite are ground up, mixed with a binder (glue) and press-molded into shape. Hemalyke has an identical chemical composition to hematite, but is less brittle.
- Hemetine is another synthetic substance that has been used for intaglios (seal rings); it is stamped rather than carved. It has the same hardness as hematite, but may include titanium oxides or stainless steel.
- A flux-grown synthetic hematite was first recorded in 1967.
Hematite is an inexpensive material.
Working with hematite
- Hematite has a conchoidal, uneven fracture and no cleavage, but there is a natural parting on two planes. The material needs to be treated carefully during polishing as it can chip.
- The low cost of hematite makes it suitable for beads, cabochons and carvings. Its softness means that it is easy to carve and it has been used for intaglios for centuries. Sometimes hematite is faceted and the upper surface of a cabochon is cut in a similar way to a rose cut. Facet edges and surfaces lose their sharpness and polish over time, so the stone will have to be repolished at some stage.
- The specific gravity of hematite is high, which means that a row of hematite beads will feel very heavy compared to one with other gemstones of the same size.
- Hematite is soluble in acid, so avoid contact with household chemicals.