Corundum · September birthstone
Sapphire
Every colour of corundum except red, and the best daily-wear coloured stone.
- Hardness
- Mohs 9
- Toughness
- Excellent
- Daily wear
- Excellent for daily rings
- Price tier
- USD 1,000 to 20,000+ per carat, fine quality
- Colours
- Blue, Pink, Yellow, Padparadscha, White, Green
- Origins
- Sri Lanka (Ceylon), Madagascar, Myanmar, Kashmir (historic), Montana, Australia
Sapphire is corundum in any colour but red. Blue is the reference, from Kashmir’s velvety cornflower (mined out a century ago) to Ceylon’s bright blues and Madagascar’s excellent value. Padparadscha, a pink-orange, is the rarest named colour. With a hardness of 9 and excellent toughness, sapphire is the ideal alternative engagement stone.
How to buy sapphire
Judge colour in daylight and under a lamp: some sapphires go grey or inky under artificial light. Avoid windows (pale see-through centres). Above one carat, buy with a laboratory report stating heating and origin.
Treatments
Heating is routine and accepted; beryllium diffusion must be disclosed.
Care
Warm soapy water and a soft brush; ultrasonic is safe for untreated and heated stones.
Lore
Medieval clergy wore sapphires as a symbol of heaven; Princess Diana’s engagement ring made the blue sapphire and diamond halo a classic.
