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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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27 of 27 gemstone entries

Quick overview

Emerald

Love emerald's green? Learn how inclusions, fillers, toughness and treatment disclosure shape how an emerald is chosen, worn, cleaned and set.

Classification
Mineral variety
Mohs hardness
7.5–8 (scratch resistance — one part of durability)
Wear considerations
Emerald is 7.5 to 8 on the Mohs scale with fair to good toughness, and it is more brittle than ruby or sapphire. Heat, ultrasonic and steam cleaning, alcohol, solvents and even jewellery repair can damage the stone or alter its filler. A bezel or surrounding accent stones help protect a ring stone from blows.
Treatment
Near-colourless oil or wax in fissures (CIBJO rates this unstable), Resin or other polymer filling of fissures (CIBJO rates this unstable), Hardened resin filling of open fractures or cavities (CIBJO rates this unstable), Dyeing with coloured oils or resins (CIBJO lists this as occasional)
Care
Clean an emerald with warm, soapy water and gentle scrubbing. Avoid ultrasonic and steam cleaners, alcohol, solvents (including some washing-up liquids) and harsh chemicals, because these can weaken the stone or alter…
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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.