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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

Topaz

Topaz is one mineral in many colours. Learn which colours are natural, which are treated, and why a hard stone with perfect cleavage needs careful setting and gentle care.

Classification
Mineral species
Mohs hardness
8 (scratch resistance — one part of durability)
Wear considerations
Topaz rates 8 on the Mohs scale, so it resists scratching well, but its perfect cleavage gives it poor toughness. A hard blow, extreme pressure, high heat or a sudden temperature change can split it. For valuable topaz, jewellers prefer protective mountings or lower-wear pieces such as pendants and pins.
Treatment
Irradiation and heating, which can turn colourless topaz blue, Heating, which can remove the yellow from yellowish pink topaz and strengthen the pink, Metal-oxide surface coating, often marketed as mystic topaz
Recognised sources
Notable locality
Care
Clean topaz with warm, soapy water, then rinse and dry it. Avoid steam cleaners and ultrasonic cleaners for topaz. Protect topaz from hard knocks, extreme pressure, high heat and sudden temperature changes,…
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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.