Sapphire

Sapphire is corundum, the same mineral as ruby. Red corundum is ruby; every other colour is sapphire. A few hundredths of a percent of iron and titanium turn colourless corundum blue. At 9 on the Mohs scale it is the hardest gem after diamond, and tough enough for a ring worn every day.

Some of the finest sapphires of recent decades are African. In 1998 sapphire was found at Ilakaka in southern Madagascar, and the island now produces blues that can rival the traditional sources.

Where the name comes from

The name comes from the Greek sappheiros.

Beliefs and legends

• The colour of the sky. An old Persian legend held that the earth rested on a giant sapphire, whose reflection coloured the sky.
• Protection from envy. Greek and Roman kings and queens believed blue sapphire protected them from harm and envy.
• A symbol of heaven. Medieval clergy wore sapphire to stand for heaven, and ordinary people believed it drew heavenly blessings.
• A pledge of faithfulness. Sapphire came to stand for truth, sincerity and faithfulness, one reason it is so often chosen for engagement rings.

The colours, and their names

• Blue: the classic. The finest is a velvety to violetish blue of medium to medium-dark tone.
• Fancy sapphires: pink, yellow, orange, violet, purple and green, each priced in its own range.
• Padparadscha: a rare pinkish orange, named from the Sinhalese word for the lotus flower.
• Colour change: blue in daylight, purple under lamplight.
• Star sapphire: fine needles of rutile make a cabochon show a six-rayed star.

Treatments, honestly

Heating is common, permanent and widely accepted: it deepens the blue and clears the fine needles inside. Some sapphires have their colour changed by beryllium diffusion, which is permanent but very hard to detect without a laboratory and must be disclosed. A few are glass-filled to hide fractures. We tell you what we know about each stone before you buy it.

How to judge a sapphire

• Colour first: strong to vivid saturation; greyish, very light or very dark blues are worth less.
• Clarity: most blue sapphires carry some inclusions but are usually cleaner than rubies.
• Cut: a good cutter balances colour against weight.
• Size: most commercial blue sapphires are under five carats; large fine stones climb steeply in price.
• Ask about treatment in writing.

Caring for your sapphire

Sapphire has excellent toughness and no cleavage. Untreated, heated and diffused sapphires can be cleaned in warm soapy water, an ultrasonic or steam. Glass-filled stones need only a damp cloth, and even lemon juice can harm them.

At a glance

Mineral	Corundum (aluminium oxide), any colour but red
Hardness	9 Mohs; excellent toughness
Colours	Blue; pink, yellow, orange, violet, green; padparadscha; colour change
From	Madagascar, Tanzania, Kenya; also Sri Lanka, Myanmar, Australia
Treatments	Heating common; some beryllium-diffused or glass-filled. Disclosed per stone
Care	Soapy water, ultrasonic, steam (except glass-filled: damp cloth)