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.
27 of 27 gemstone entries
Explore birthstones. Some months have several recognised stones and birthstone traditions vary. Association does not determine suitability, value or availability.
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Quick overview · June birthstone
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.…
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.