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A Guide to Pearl Qualities and Grades

Author: The Pearl Market.
Buying pearls can be confusing - there are many myths, misconceptions and misleading pieces of information (see buying pearls - tricks and traps). One thing is certain. The romantic image of the pearl fisherman diving off the side of a small boat to harvest pearls from the ocean floor is gone. Perhaps it's just as well. Pearl diving was a dangerous occupation that claimed many lives. Wild pearls still exist but are difficult to find. Nowadays, pearls are cultivated in freshwater lakes and rivers or seawater rafts.

Shape near round mostly round round
Lustre fair good high
Surface < 75% clean > 75% clean > 90% clean
Nacre 0.25 to 0.35mm 0.35 to 0.5mm over 0.5mm
Matching fair good very good
Pearl Grades
Grading takes into account shape, lustre, surface quality, nacre thickness and matching on the strand. There is no international standard for grading pearls so identical pearls may be graded differently by different suppliers.

Grading a strand of pearls like a necklace is slightly different to grading individual pearls as not every pearl on the strand will necessarily meet all the criteria.

The pearl industry has it's own jargon but most reputable pearl sellers use the A, AA, AAA grading system (Tahitian pearls may also use an A to D system) and follow accepted industry conventions. If you want to dive deeper into the world of pearls use this glossary of terms as a reference.

Shape: pearls develop into a variety of shapes. Round pearls are the rarest and the highest priced. The term 'round' does not mean spherical like a marble but the pearls should not look obviously oval or flattened to the naked eye.
pearl shapes
It's worth remembering that non-round pearls can offer a lot of pearl for your money. Wild pearls are rarely round so different shapes could be thought more natural.

Lustre: is the shine that gives pearls their beauty and is an important buying factor. Lustre refers to the pearls brilliance - the way it's surface reflects light, and to it's inner glow - how it refracts light from the layers of nacre within.
pearl lustre
Pearls with low lustre appear chalky, yellow or dull. This example gives an idea of the lustre expected from the three grades. Different types of pearl exhibit different types of lustre. For example, bead nucleated pearls with relatively thin nacre may look 'shiny' whereas thick nacre pearls, like South Sea and freshwater pearls, have more of a glow.

Poor lustre pearls are sometimes coated or laquered to improve their appearance but such treatments are only a temporary fix.

Surface Quality: pearls are a natural product and, like handblown glassware, small natural imperfections are quite acceptable - even desirable. Unacceptable faults include cracks or holes in the surface and thin or flaking nacre.
pearl blemishes
Grade AAA at least 95% clean
Grade AA at least 75% clean
Grade A less than 75% clean

Pearls which are completely clean - with no scratches, pits, bumps or wrinkles visible to the naked eye - may be designated 'spotless'.

Matching: compares all the pearls on the necklace with each other to see how they match. They don't have to be identical - that can seem artificial and real pearls will vary a little. Most people can judge when something looks wrong, for example, a necklace of 7-8mm pearls where the larger pearls are grouped to one side or a small pearl is sandwiched between two bigger ones.

pearl matching Examine a necklace by placing it on a light cloth background in soft natural daylight. Not indoor lighting, UV displays or direct sunlight. Is the lustre good or are the pearls chalky, yellow or dull? Naturally coloured necklaces can have variations in tone but they shouldn't be glaring.

Turn the necklace in your hands and inspect it from different angles. Use the grading factors above to make a judgement but don't overdo the analysis. If it looks ok it probably is!

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Seawater pearls are cultivated by implanting an oyster with a mother-of-pearl shell bead. This is called the 'nucleus'.

To protect itself, the mollusc coats the bead with layers of nacre. The longer the bead stays in the oyster the more the layers of nacre and the finer the pearl.

seawater pearls
Seawater pearls should remain in the ocean for at least two years to develop sufficient layers of nacre.

In recent times commercial pressure has resulted in farms harvesting their pearls early, but if a pearl is harvested too soon the thin nacre covering the bead will be prone to cracking and flaking.

Nacre thickness is one reason seemingly identical pearls may be priced differently. On seawater pearls look for a nacre covering of at least 0.3mm, preferably 0.5mm plus.

Freshwater pearls use a different culturing technique and take up to six years to grow.

freshwater pearls
Molluscs are implanted with small pieces of tissue instead of a shell bead. When harvested, the tissue has gone, leaving a solid pearl. Nacre thickness isn't an issue with freshwater pearls.

wild pearls

wild pearls
Come in all shapes, colours and sizes. As their name implies, wild or natural pearls are formed without the intervention of man. Overfishing and pollution has eliminated most wild oyster beds but some can still be found in the waters of the Arabian Gulf.

Wild pearls are prized by connoisseurs and a necklace made with natural pearls will be worth many times more than it's cultured pearl equivalent.
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