AKOYA PEARLS – Renowned for their lustre, these cultured saltwater pearls are the pearls most often used in expensive 'high-end' necklaces. They are generally white or cream-colored. They also tend to be the most consistently round and near-round pearls. Originally produced exclusively in Japan, there are now Chinese Akoya pearls in the market.

CULTURED PEARLS – Pearls that are grown inside a mollusc when a foreign item has been surgically implanted by human means. Cultured pearls are grown on pearl farms where several thousand molluscs can be implanted and cared for over the 2-5 years required for a pearl to develop. Cultured pearls were generally thought of as expensive, high-end pearls, and the word is still used widely with that higher value in mind. But in a sense, all pearls grown on pearl farms are cultured – the word simply refers to those grown with human intervention rather than occurring randomly in nature.

FRESHWATER PEARLS – Pearls that come from freshwater molluscs (not oysters, which are in salt water only) and that are cultivated in lakes and rivers, not in the ocean. They are often somewhat less lustrous than their saltwater counterparts. However, they appear in a wide variety of shapes and colours, and they tend to be less expensive than saltwater pearls, making them quite popular. Freshwater pearls are also quite durable, resisting chipping, wear, and degeneration.

A single mollusc can produce up to 50 pearls. The quality of freshwater pearls is improving each year, and it is getting more difficult to tell the difference between them and their saltwater cousins.

IMITATION (FAUX, FAKE) PEARLS – Simulated pearls manufactured entirely by man or machine. They have no real value as a gemstone. They can be made from glass, ceramic, shell, or even plastic. The bead is then coated with varnish and/or other materials in order to produce a pearl-like lustre and iridescence.

A common test to determine whether a pearl is genuine or imitation consists of scraping the pearl gently across one's teeth. Imitation pearls feel smooth to the tooth, while genuine pearls feel slightly gritty or abrasive. Also, if the pearls are perfectly smooth, round and uniform, they are likely imitation pearls, unless you have paid £5,000 for the strand!

MOTHER-OF-PEARL - The basic substance that is secreted by oysters and molluscs to form the inside of their shells. It is the same substance that also forms pearls.

NATURAL/WILD PEARLS – Pearls that are formed more or less randomly in nature when some sort of irritant becomes lodged in the tissue of an oyster or mollusc. In response to the irritation, the oyster secretes nacre, which gradually builds up in layers around the irritant. Over a period of several years, this build-up of nacre forms a pearl. Now very rare, and often collected illegally.

SALTWATER PEARLS – Pearls that come from molluscs that live in saltwater, the most well-known of which are oysters. Traditionally, pearls in past generations were almost all saltwater pearls. But these days, the majority of pearls are freshwater pearls. Saltwater pearls tend to be rounder and have richer tones, and still fetch a much higher price. Expect to see saltwater pearls on knotted beading silk as this reduces wear on the individual pearls. The most expensive pearls in jewellery shops are usually saltwater pearls.

Shape is one of the important factors determining the quality and value of a pearl. The most valuable pearls are round. However, other shapes of pearls include near-round, drop, potato, oval, button, nugget, rice and baroque. Freshwater cultured pearls are grown in all of these shapes as well as new, creative forms such as stick, angel-wing, cross, heart and coin shapes.

BAROQUE PEARLS – Pearls that are both non-symmetrical and irregular in shape. Used as a general term for any shape that does not fit other categories! Also sometimes called 'nugget' or 'pebble' pearls.

Can include pearls shaped like popcorn, peanuts, bullets, rocks and so on.

BUTTON PEARLS – Button pearls are round pearls that are flattened to some degree, making them resemble a button or perhaps a disk rather than a perfect sphere. Often they are flat on one side. They tend to be quite uniform, and are popular as spacers.

DROP (TEARDROP, PEAR) PEARLS – Pearls that are pear or teardrop-shaped. The drop can either be "long" or "short," depending on its proportions.

These pearls make attractive earrings or pendants.

KEISHI PEARLS - Keishi pearls are formed when the oyster rejects the implanted nucleus before the culturing process is complete, or form after the cultured pearls have been removed. These molluscs eventually produce pearls without a nucleus that are 100% nacre. Keishi come in a wide variety of colours, and tend to be very lustrous. They are 'petal' or 'cornflake' shaped irregular pearls - the word keishi means poppy seed in Japanese, and these pearls are often also referred to as 'poppy seed' pearls.

MABE (DOME, BLISTER) PEARLS – (pronounced "mah-bay") - A hemispherical shaped pearl which is grown against the inside of the oyster's shell, rather than within its tissue. The pearl develops into a dome form with a flat back – the back is usually attached manually after harvesting. Cultured mabes are used for such things as rings and earrings, rather than for stringing on necklaces.

NEAR-ROUND PEARLS – Pearls that are not perfectly round, but almost. Instead, they are slightly flattened or elongated, rather than being a perfect sphere. Nonetheless, they are so nearly perfect that they are classified as round pearls. Only a tiny percentage of “round” pearls are perfectly round – most round pearls are slightly off-round anyways. Closeness to round is one of the important factors determining the value of a pearl.

NUGGET/PEBBLE PEARLS - Pearls with an irregular shape resembling stones or pebbles. The surfaces can be smooth or rough. Except for larger, quality nuggets (also classified as “baroque”), nugget pearls tend to be on the lower price scale. There is a wide variance of quality among nugget pearls – those with blemishes, wrinkled surfaces and jagged edges should be selling at a very low price!

OVAL PEARLS – Elongated roundish pearls with curved lines that are oval-shaped like an egg, narrower at the ends than in the centre. They are sometimes also referred to as “rice” pearls. But they are the best-shaped and highest-valued form of rice pearls, and are quite often so beautiful that they deserve a more dignified classification!

POTATO PEARLS – Round-ish pearls with a slightly oblong shape and less-symmetrical curves, resembling more a potato than a sphere. Most potato pearls are freshwater cultured pearls from China. They are a very affordable substitute for round pearls, and are popular with jewellery-makers for that reason. Larger potato pearls with good surface and lustre still make gorgeous necklaces. There is a wide variance in quality among potato pearls, with the lowest quality characterized by rings or grooves and bad shape, and the highest quality being almost on par with near-round pearls.

RICE PEARL – An elongated freshwater pearl with a crinkled or ringed surface, many of which resemble a grain of rice. The more oval-shaped the pearl, the higher the value, especially if it does not have rings or other surface imperfections. The more wrinkled the surface, the lower the value, making these some of the cheapest pearls available on the market.

ROUND PEARLS – Pearls that are almost perfectly spherical, which is the shape most people think of when they think of a pearl. Because of their relative rarity and "classic" nature, they are highly desirable. The rounder, the better! But as the shape approaches closer to round, the price can rise exponentially. “Round” classification can include pearls that are “near-round” or “almost-round”, and it is sometimes difficult to know where to draw the line between “round” and “potato.”

The quality or value of a pearl is measured according to a combination of several different factors: the type of pearl, its lustre, the cleanliness and texture of its surface, its shape (the rounder the better), its colour, and its size.

BLEMISH – Any surface defect on a pearl. Blemishes can include spots, bumps, pits, holes, cracks, chips, wrinkles and dull spots.

COLOUR – One of the most important factors in classifying pearls. While pearls traditionally were thought mainly to be white (with some exquisite pinks and blacks also well-known), nowadays pearls come in all colours. The most common are still white (which are often bleached at source), and there are many shades of natural colour pearls (ranging from peach to champagne to rose to purple). And dyeing techniques have advanced to the point that pearls are now available in any colour of the rainbow, some of which are quite dazzling. Normally, the dyeing process involves soaking the pearls for a day in dye until it permeates the inside of the pearl; then baking the colour in so it won’t rub off or fade.

DYEING – A type of treatment that changes a pearl’s colour. It is usually used to create pearls with colours that cannot be made naturally, including dazzling metallic green, bright orange, wine purple, and so on.

LUSTRE – One of the most important factors determining the value of a pearl, lustre refers to the reflective quality or brilliance of the surface of a pearl.

Lustre is related to the thickness and quality of the outer layers of nacre which capture and throw back the light, giving pearls their unique and awesome “glow.” The more lustrous the pearl, the more it shines and reflects light and images. The more brilliant and mirror-like the surface of the pearl, the higher its quality and value. Pearls with low lustre appear white or chalky, rather than brilliant and shiny. Though lustre is not the same as “surface”, the two are related and the lustre is usually diminished by surface imperfections.

NACRE – (pronounced “nayker”) - Also known as mother-of-pearl, it is a combination of calcium carbonate and organic substances secreted by certain species of mollusc. It is used both as a means to smooth the animal’s shell and as a defence against irritation caused by foreign objects. The nacre is the essential material forming the outer layers of pearls, and a pearl’s value is partly determined by the thickness of the nacre.

RINGS (CIRCLES) – A surface quality that consists of concentric indentation or rings that develops on some pearls. This usually brings down the overall quality and value of a pearl. The deeper the rings (they can more accurately be called grooves!), the lower the value. But many creative designers often see special beauty and uniqueness in the rings. The rings are sometimes called 'growth rings' or even 'love rings'.

SIZE – One of the important factors determining the quality and value of a pearl. Size descriptions are expressed in millimetres, and typically apply to the diameter of a pearl. Pearls over 8mm are usually considered “big”, and the bigger the pearl, the more valuable it can be. However, it is more difficult to find perfection in bigger pearls.

SURFACE - One of the important factors determining the quality and value of a pearl, referring to the amount of blemishes on the surface. Few pearls are perfect, but the surface should be smooth and clean, without bumps, spots, discolorations, or other disfiguring characteristics. It should also be shiny and reflective, rather than dull and chalky. “Luster” is not the same as “surface” but is nevertheless affected by surface imperfections