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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

Labradorite

Labradorite is a feldspar whose best pieces flash blue, green or gold against dark grey. Learn how the flash forms, how to judge it and how to wear it.

Classification
Mineral variety
Mohs hardness
6–6.5 (scratch resistance — one part of durability)
Wear considerations
Labradorite rates 6 to 6.5 on the Mohs scale. It is brittle and has perfect cleavage, so it can break on impact. It scratches more easily than diamond, ruby, sapphire and emerald. For moonstone, a related feldspar, makers usually choose pendants, earrings and pins over rings, because rings take more knocks.
Treatment
Typically untreated
Care
For moonstone, a related feldspar, GIA names warm, soapy water as the only recommended cleaner and never recommends ultrasonic or steam cleaners. The sources for this entry give no separate cleaning guide…
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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.