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.
3 of 27 gemstone entries
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Salt-and-pepper diamond
Hardness 10
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Sapphire
Hardness 9
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Spinel
Hardness 8
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Quick overview
Spinel
Why spinel? This entry explains its long history as a stand-in for ruby, its colour range, how often it is treated, and how it holds up in everyday jewellery.
- Classification
- Mineral species
- Mohs hardness
- 8 (scratch resistance — one part of durability)
- Wear considerations
- Spinel is 8 on the Mohs scale and has good toughness, so it is durable enough for all types of jewellery. High heat can fade some spinel colours, but it is stable when exposed to light and chemicals.
- Treatment
- Heat treatment to change colour (much less common than in ruby; stable in normal wear). Named here as this guide's editorial practice, not as a statement of any country's law., Fracture filling (rarely done; filled stones need gentle cleaning). Named here as this guide's editorial practice, not as a statement of any country's law.
- Care
- Warm soapy water is always safe for spinel. If a stone may have been fracture filled, clean it only with warm soapy water or a damp cloth. Ultrasonic and steam cleaners are…
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.