Skip to content

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.

Explore birthstones
More filters

27 of 27 gemstone entries

Quick overview

Laboratory-grown moissanite

Laboratory-grown

Moissanite is silicon carbide. Gem-quality natural moissanite has never been found, so moissanite gems are made in a laboratory. It is very hard, shows strong rainbow fire and has optical properties that set it apart from diamond.

Classification
Laboratory-grown material
Mohs hardness
9.25 (scratch resistance — one part of durability)
Wear considerations
Moissanite is 9.25 on the Mohs scale and its toughness is listed as excellent. It is very hard and durable, though not as hard as diamond. In a hammer test, a moissanite cube shattered, so a hard blow can damage it.
Treatment
Treatment not usually encountered
Care
Moissanite resists most chemicals, and in GIA’s 1997 study the manufacturer reported no problems with conventional cleaning. The metal and any other stones in your piece may need different care, so follow…
Explore the full gemstone guide Read the buying guide

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.