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Gemstone encyclopedia

Every gemstone, explained

What each stone is, how it wears in jewellery, and what to ask before you choose one. Browse by colour, or go straight to a letter.

This encyclopedia is educational. Inclusion does not confirm current Ralph Jacobs stock, sourcing, availability or suitability for a particular jewellery design.

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Quick overview · June · Alexandrite variety, as listed by GIA alongside pearl and moonstone

Chrysoberyl

Chrysoberyl is the mineral of cat's-eye chrysoberyl and alexandrite. It rates 8.5 on the Mohs scale and is commonly untreated. Aligned needle-like inclusions can give it a sharp eye.

Classification
Mineral species
Mohs hardness
8.5 (scratch resistance — one part of durability)
Wear considerations
Rates 8.5 on the Mohs scale. Alexandrite is usually rated tough with no cleavage, and the cat's-eye very durable, but one mineral reference lists distinct cleavage and brittle tenacity, so sharp knocks can still cause damage.
Treatment
Irradiation to change colour (rare, in cat's-eye; some stones may be radioactive), Filling of fissures with oils, wax or resins (rare, in alexandrite; CIBJO classes these fillings as unstable)
Care
Warm, soapy water is described as always safe for alexandrite, and it is a simple way to clean any chrysoberyl at home. Ultrasonic and steam cleaners are usually safe for untreated stones.…
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Individual gemstones vary. Care depends on treatment, setting and condition. Encyclopedia inclusion does not confirm availability.

Individual gemstones vary · care depends on treatment, setting and condition · birthstone traditions vary · encyclopedia inclusion does not confirm availability.