What is a sapphire gemstone?
By Jared James · Last updated 21 May 2026
Definition
Sapphire is a variety of corundum, the same mineral family as ruby, and it comes in almost every colour imaginable: the most famous is blue, but sapphires are also found in pink, yellow, orange, white, teal, violet and black. The only colour corundum cannot be called sapphire is red, because red corundum is ruby by definition. Sapphire scores 9 on the Mohs hardness scale, making it the second hardest natural gemstone after diamond, which is why it is so well suited to rings and other jewellery that takes daily wear. It is also the birthstone for September.
Frequently asked questions
- What colours do sapphires come in?
- Sapphires come in blue, pink, yellow, orange, purple, teal, white and black. The orange-pink variety is called padparadscha, which is one of the most valuable. Blue remains the most popular and most associated with the name, but coloured sapphires, especially pink and teal, are increasingly sought after in engagement rings.
- Are sapphires good for engagement rings?
- Sapphire is one of the best gemstone choices for an engagement ring because of its hardness. At 9 on the Mohs scale it handles everyday wear and knocks far better than most other coloured gems, which typically sit at 7 to 8. Princess Diana's and Kate Middleton's famous sapphire ring helped make blue sapphire engagement rings a perennial favourite.
- Are most sapphires heat-treated?
- Yes, the majority of sapphires on the market are heat-treated to improve their colour and clarity, which is a standard, accepted practice in the gem trade. Untreated sapphires with strong colour and good clarity are rarer and command a significant premium. Reputable sellers will disclose treatment.
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