Pearls

A pearl is grown, not mined. Inside an oyster or mussel, a pearl sac builds up layer after layer of nacre, mostly calcium carbonate, until a pearl forms. A natural pearl starts by chance; a cultured pearl starts when a skilled technician places a small piece of mantle tissue, often with a shell bead, inside the mollusc.

Almost all pearls sold today are cultured. We stock three kinds: Akoya, freshwater and Tahitian.

The three pearls we sell

Akoya pearls are the classic white or cream pearls of a traditional strand. They grow in a small saltwater oyster in Japan and China, are usually round, and range from about 2 to 11 millimetres, most often 6 to 8.

Freshwater pearls grow in mussels in lakes and ponds, mostly in China, often many pearls to one mussel. They come in the widest range of shapes, sizes and colours, at the gentlest prices.

Tahitian pearls grow in the black-lipped oyster, mainly around French Polynesia. They are often called black pearls, but their colours run from black and dark grey to silver, with overtones of green, blue, pink and purple. A dark green-grey with a pink-purple sheen is called "peacock".

Beliefs and legends

• Cleopatra's wager. The Roman writer Pliny tells how Cleopatra bet Mark Antony she could spend a fortune on a single banquet, then dissolved one of her great pearl earrings in vinegar and drank it. Historians still debate whether it happened, but a pearl will indeed dissolve in vinegar.
• Children of the moon. Many cultures linked the round, glowing pearl with the moon.
• Against fire and dragons. In ancient China, pearls were said to protect their owner from fire and from fire-breathing dragons.
• Purity. In Europe, pearls stood for modesty and purity.

Treatments, honestly

Some pearls are treated to change their colour. Freshwater and Akoya pearls may be irradiated or dyed to produce greys and darker shades. Dye often shows as colour gathered around the drill hole. We tell you what we know about each pearl's colour before you buy it.

How to judge a pearl

GIA judges pearls by seven value factors:

• Lustre, perhaps the most important: bright, sharp reflections rather than a dim glow.
• Surface: fewer and smaller marks.
• Shape: round is the rarest and usually the most valuable, but well-formed ovals, pears and baroques are prized too.
• Colour: the body colour, plus any overtone and orient (iridescence).
• Size: larger is rarer.
• Nacre: thick enough that the bead does not show and the pearl does not look chalky.
• Matching: pearls in a strand or a pair of earrings should match.

Caring for your pearls

Pearls are soft (about 2.5 on the Mohs scale) and easily scratched. Put them on last, after perfume, hair spray and make-up, which can damage them, and take them off first, wiping them with a soft cloth. Clean them only in warm soapy water, never in an ultrasonic or steam cleaner, and let a strand dry completely before you wear it. Keep them away from strong heat and light, which can dry out and crack the nacre.

At a glance

Material	Nacre (calcium carbonate and conchiolin), grown by molluscs
Hardness	about 2.5 Mohs; very soft
Types we sell	Akoya (Japan, China) · freshwater (China) · Tahitian (French Polynesia)
Colours	White, cream, grey, black; pink, green, blue and purple overtones
Treatments	Some irradiated or dyed. Disclosed per pearl
Care	Last on, first off. Warm soapy water only