Sapphire is the gemstone variety of corundum, made primarily of aluminium oxide (Al₂O₃) with tiny amounts of other elements that create its colour.

• Blue sapphire gets its colour from traces of iron and titanium.
• Other colours – yellow, pink, green, teal, peach, purple – come from different trace elements and combinations.
• When corundum is red, we call it ruby, even though it’s the same mineral family.

Sapphire is prized for its durability, crisp optics and the way it holds colour in both daylight and evening light.

Family: Corundum

Hardness: 9 (excellent for everyday wear)

Colours: Blue, teal, green, yellow, pink, purple, peach, parti-colour

Birthstone: September

Traditional meanings: Wisdom, loyalty, protection, truth

Why I love it: Strong, structured and luminous – a gem that carries both calm and intensity, perfect for clean, contemporary designs with a personal edge.

• Mineral: Corundum
• Chemical composition: Al₂O₃ with trace elements
• Crystal system: Trigonal
• Hardness: 9 on the Mohs scale (second only to diamond)
• Refractive index: ~1.76–1.77
• Specific gravity: ~3.95–4.03
• Lustre: Vitreous (glass-like)
• Typical cuts: Oval, cushion, round, emerald cut, step-cut baguette, fantasy cuts and contemporary freeforms

Optical notes:

• Often pleochroic – it can show slightly different colours from different directions.
• May display colour zoning – bands of different saturation that I sometimes highlight rather than hide.

Sapphires appear in a wide palette:

• Classic blue – from soft cornflower to deep inky midnight
• Teal & greenish-blue – modern, moody, often Australian or Montana material
• Pink & peach – from delicate ballet pinks to warm “sunset” tones
• Yellow – citrus, honey and golden hues
• Parti sapphires – stones that show more than one distinct colour at once, such as blue and yellow or green and gold in a single gem

Special varieties you might hear about:

• Padparadscha sapphire – a rare blend of pink and orange, named after the colour of a lotus blossom
• Star sapphire – a cabochon-cut stone where fine rutile needles create a visible star under a single light source

Across cultures, sapphire has been linked to:

• Truth, loyalty and wisdom
• Status and protection in royal and ceremonial jewellery
• In medieval Europe, it was thought to guard against envy and harm, and to keep the wearer honest in word and deed

Sapphire is the traditional birthstone for September and a beloved choice for engagement jewellery for those who want something timeless but less expected than diamond.

Many sapphires in the market are treated. That isn’t automatically “bad”, but it should always be disclosed.

Common treatments:

• Heat treatment – used to improve colour and clarity; generally stable and accepted in the trade when transparent about it
• Diffusion and other advanced treatments – used to alter colour more dramatically (for example, surface diffusion of elements); these affect value and should always be clearly declared

In my own practice I favour natural sapphires and carefully chosen heated stones, with full disclosure. Whenever possible I look for traceable, responsibly sourced material,