Buying guide

Corundum

Purple corundum is purple sapphire under a more cautious trade name. The material offers Mohs 9 durability and genuine rarity at a fraction of blue sapphire pricing.

Corundum at a glance

Mineral family: Corundum
Chemical formula: Al2O3
Mohs hardness: 9
Refractive index: 1.762 - 1.770
Specific gravity: 4.00
Crystal system: Trigonal
Colours: purple, pink
Birthstone month: September
Anniversary: 5th & 45th
Typical treatment: Commonly heat treated. Disclosure of diffusion treatment is essential.
In stock now: 4 stones from $77.50

What drives the price

Purple corundum is purple sapphire under a more cautious trade name. The material offers Mohs 9 durability and genuine rarity at a fraction of blue sapphire pricing.

In one line: Colour saturation, treatment status, size.

Treatment

Commonly heat treated. Disclosure of diffusion treatment is essential.

Any seller unwilling to state treatment in writing is telling you something. Every listing on this site states it.

Durability and daily wear

Extremely durable at Mohs 9. Ultrasonic and steam safe.

Mohs 9, trigonal crystal system, specific gravity 4.00.

Tradition and meaning

Purple corundum bridges the heart and higher mind, associated with insight and calm discernment.

Birthstone for September. Associated with Virgo and Libra. Anniversary stone: 5th & 45th.

Frequently asked

Is purple corundum the same as purple sapphire?

Chemically and gemmologically, yes, both are gem-quality aluminium oxide. Sellers sometimes prefer corundum when a stone has not been lab-certified, so the term often signals caution rather than a lesser stone.

Is purple corundum rare?

Fine purple corundum is scarcer than blue sapphire in comparable qualities, but it attracts far less demand, which keeps prices well below what its rarity would otherwise justify.

How durable is it?

Identical to ruby and sapphire, Mohs 9, no cleavage, excellent toughness. It is among the most wearable coloured stones available.