How Pearls are Formed

Some believed pearls to be the tears of the gods. Others thought them dewdrops filled with moonlight that fell into the ocean and were swallowed by oysters.

A pearl is a natural gem created by a living organism. When a foreign object is introduced into a mussel or oyster the animal coats the irritant with a substance called nacre, the same material with which it builds it's shell. Layers of nacre build up to make a pearl.
   Pearl Guide
pearl history a brief history of pearls
how pearls are formed how pearls are formed
pearl qualities and grades pearl qualities and grades
pearl shapes and colours pearl shapes and colours
pearl sizes pearl sizes and comparisons
choosing and caring for pearls choosing and caring for pearls
buying pearls buying pearls - tricks and traps
Cultured Pearls

Most wild, natural pearl producing oyster beds have vanished due to over-fishing, oil drilling and pollution. Today, the world's most beautiful pearls are cultured.

Cultured pearls share the same properties as wild pearls. The difference is that a technician opens the shell and inserts the irritant which stimulates nacre production.

Seawater oysters have a round shell bead (traditionally from an American freshwater mussel) grafted in as the irritant. This is called 'nucleating'. Oysters are suspended in water from rafts and at risk from typhoons, parasites, predators and algae.

Freshwater mussels have a small piece of mantle tissue (nacre producing tissue from another mussel) introduced as the irritant. This tissue dessicates leaving a solid pearl. Mussels are farmed in inland lakes and rivers.

Harvesting and Processing Pearls

Harvesting pearls is a time consuming business. Of the millions of oysters and mussels seeded each year, only a proportion (maybe just 50%) will survive to bear pearls. Of these, many will not produce pearls of a marketable quality.

sorting pearls
Each pearl must be sorted by size, shape, colour, lustre and blemish.pearl drills

Then they need to be drilled and matched for stringing - a skilled and laborious task.

To find 50 perfectly matched high-quality pearls for a 16 inch necklace a pearl processor may have to sort 10,000 pearls.

Now you know why good quality pearl necklaces aren't cheap !
Pearl Colours

Pearls come in a variety of colours. Natural colours are mainly down to to the breed of mollusc. Other influences include diet, water temperature and pollutants.

pearl colours
No-one can predict or control what colour pearls will be produced in any hatchery.

Black pearls are rarely jet black but blue, green, grey, aubergine, peacock and more. Green is the predominant colour.

black pearls
Naturally coloured black pearls come from the pearl farms of French Polynesia (Tahitian pearls) as well as Indonesia and the Phillipines.

Except for freaks, there are no natural black freshwater or Akoya pearls though these may be dyed or irradiated to simulate black pearls.

Many people think of wild oysters ingesting a grain of sand as the foreign body which stimulates nacre production.

Living in the sea, oysters are constantly ingesting and expelling sand and irritants.

Only when something becomes lodged - like a piece of shell, bone, coral or parasite does the oyster start nacre production.


Is made of crystals of calcium carbonate alligned with each other so that light passing along the axis of one, is reflected and refracted by the other to produce a rainbow of light and colour.
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