Hambergite Hambergite is one of the lesser-known gemstones. It is usually almost colorless, with the vitreous luster of glass when cut. It is quite a hard material, with a hardness of 7.5 on the Mohs scale, so it takes a very good polish. Hambergite derives its name from the Swedish geologist and geographer Axel Hamberg (1863-1933).
There are several features that make hambergite quite unique. It has very strong double refraction, with a birefringence rating much higher even than zircon. Hambergite also has a low density, but a high refractive index, a combination that is very unusual in the gemstone world.
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