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Understanding Pearls

A pearl is created by a mollusk when an irritant causes it to secrete alternating layers of material, called "conchiolin" and "nacre", to coat the invader and make its presence less bothersome. This irritant forms the nucleus of the pearl. With natural pearls, this irritant is probably a parasite or a piece of debris that the animal is unable to wash away. Nearly all pearls on the market are "cultured" pearls, where a relatively large bead is placed in the body of the host oyster (cultured saltwater pearls) or a small piece of tissue from a fresh water mussel is inserted into another mussel to stimulate pearl formation (freshwater pearls).

Pearls are classified by Origin, then graded by size, shape, nacre thickness, color, luster, surface clarity and matching. These qualities are not considered equal. Some factors will be weighted to give them more influence in arriving at a final grade. A very thin nacre thickness, for example, could never yield a fine quality pearl.

Grading is relative to the best attainable quality for the type. For example, South Sea pearls, which grow in warmer water for longer periods of time, generally have a lower luster and more tiny blemishes than Japanese Akoya pearls, that grow in colder water and for shorter periods of time. South Sea pearls are graded against each other, not by what would be expected for a similar quality Akoya pearl.

Origin:

• Cultured (Akoya)- the traditional cultured pearl, farmed almost exclusively in Japan.
• South Sea cultured - Large cultured pearls from Tahitian and other South Sea waters including Australia, these are mostly white to silver-white, gray and golden in color. They are grown in the Margaretifera oyster, and are considerable larger than the Japanese Akoya oyster pearl.
• Tahitian cultured- Gray to black colored pearl cultivated in the black-lipped variety of Margaretifera oyster found in the south Pacific.
• Freshwater cultured- nucleated with tissue only, with no bead nucleus, these mostly irregular, colorful pearls are farmed in Japan, China and the United States, among other locations. They are nurtured in freshwater mussels rather than oysters.
• Novelty- pearl-like concretions formed by mollusks other than oysters and mussels, such as abalone, clam or conch.
• Natural- occurring naturally in the mollusk without assistance from man. Also referred to as "Oriental" pearls. These now constitute only a tiny portion of the pearl market.

Size: A large pearl can be produced only by a mollusk large enough to hold it. Thus, the pearl farmer has a significant investment in raising the mollusk before it can even be nucleated. Because of this, size is a significant factor in valuing pearls.

Shape: This refers to the roundness or symmetry of the pearl. Round pearls are the rarest and most highly prized. Even though they start with a round bead, the action of the mollusk and movement of the water usually cause the pearl to become a shape other than perfectly round. Symmetrical pearls of other pleasing shapes are rated for symmetry, but priced according to a different scale from rounds.

• Round - Rated as Round-in-all, Mostly Round, Slightly Off-Round, Off-Round and Semi-Baroque. (Baroque pearls are considered a separate category.)
• Drop - a pear- or teardrop shaped pearl. The more symmetrical, the higher the quality.
• Barrel - more or less cylindrical, with blunt ends.
• Ringed - pearls that have developed attractive grooves by being turned ‘round and ‘round in the oyster in one place.
• Baroque - pearls with a pleasingly organic shape, without ‘tags’ or sharp tails.

Nacre Thickness: Nacre is the single most important factor in the beauty and durability of the pearl. If you can see the bead through the nacre, or if it is cracked or peeling or has chalky-looking patches, it is a very low grade pearl. Some pearls with thin nacre have high luster and are free of blemishes, because they have been left in the water for only a brief time. This thin surface will soon be damaged by normal wear, and may chip or peal around the drill hole. Always look for pearls with at least Medium nacre, at least 0.35 mm thick.

Luster: The brightness, or reflectivity of the pearl. The very top pearls have a metallic luster, while fine pearls have a sub-metallic luster but still reflect objects sharply on the surface. Low-luster pearls display very little if any reflectivity.

Color:

• Body color - the base color of the pearl, observable near the outer edges of the pearl.
  White and silver-white are the preferred colors, with grays and cream colors being less desired. However, color is a personal preference and should be chosen to complement skin tone.
• Overtone - one or more colors that may (or may not) overlay the body color. Best observed just off the dome of the pearl. Pink overtones are preferred, with green and other colors less desirable.
• Orient - play of color, or iridescence seeming to move about the surface of some pearls. It is a rare component, more often seen on irregular surfaces.

Surface blemishes, or texture: Surface blemishes, or texture refers to blemishes or spotting on the surface of the pearl. They are graded by their size, type, number, location and visibility.

Matching: refers to pairs or strands, and addresses uniformity of color, luster, shape, spotting and graduation. If colors are intentionally mixed, it refers to the attractiveness of the combination. Even in ‘uniform’ strands, there will be gradation in size from the center pearl to those at the ends. Each pearl in a strand has been selected to be placed between its neighbor on each side, and there should be no noticeable difference between pearls that are side-by-side. Bead stringer not trained in stringing pearls may inadvertently re-string pearls in the incorrect order, disrupting the imperceptible ‘blend’ of one pearl to the next and decreasing the value of the strand.

Pearl mounting/stringing: a perfectly blemish-free pearl is usually not drilled, but rather is mounted in prongs or glued in place. If the pearl is perfectly "clean" except for one blemish, a drill hole will be placed through the blemish. Pearl beads are drilled though one, or sometimes two blemishes, to yield the best quality possible. Pearl strands should be knotted to prevent them from wearing against each other and to reduce loss in case the strand breaks. Knots should be tight against the pearl. If a pearl can slide between knots, it is a sign that the string has stretched and needs to be replaced. If a mounted pearl begins to wobble or turn, stop wearing it immediately and take it to your jeweler to have it re-glued.

Condition: The surface of the pearl should be smooth and not abraded by chemicals such as perfume, hair spray, and skin acids. There should be no peeling or cracking of the nacre layer around the drill hole. Pearls that have been stored in a safe deposit box for long periods may have yellowed.

Pearl care: Protect pearls from chemicals and abrasion. Pearls are very soft, and are easily damaged by other jewelry. Most dust contains much harder quartz particles. Thus, pearls are easily scratched by careless cleaning. Keep pearls in their own soft case or bag, and wait to put them on until your hair, make-up and perfume have all been applied. After wearing them against the skin, wipe pearls gently with a very soft, damp cloth before returning them to their secure haven. As pearls seem to benefit from exposure to the light, remember to wear them often!

PEARL GRADING NOMENCLATURE

Pearls are classified by Origin, then graded by size, shape, nacre thickness, color, luster, surface clarity and matching. These factors are weighted to arrive at a final grade.

Size: Limited by the mollusk used in cultivation, size is a very significant factor in valuing pearls.

Shape: Refers to the symmetry and form of the pearl. Fancy shaped pearls, such as drops, buttons, coin, barrel, ringed (ridged) etc. are graded according to their symmetry and balance.

(Rounds)

(Baroques)

Nacre Thickness: Nacre is the single most important factor in the beauty and durability of the pearl Some pearls with thin nacre have high luster and are free of blemishes, because they have been left in the water for only a brief time. This thin surface will soon be damaged by normal wear, and may chip or peal around the drill hole.

Luster: The brightness, or reflectivity of the pearl. The very top pearls have a metallic luster, while fine pearls have a sub-metallic luster but still reflect objects sharply on the surface. Low-luster pearls display very little if any reflectivity.

Color: Color is described by the base color of the pearl, called body color, and any additional colors that may be overlaying the base color, called overtone. These grades reflect demand in the US market, but pearls should be selected to complement the skin tones of the person who will be wearing them.

Surface blemishes, or texture: refers to blemishes or spotting on the surface of the pearl. They are graded by their size, type, number, location and visibility.

Matching: refers to pairs or strands, and addresses uniformity of color, luster, shape, spotting and graduation. If colors are intentionally mixed, it refers to the attractiveness of the combination. Each pearl in a strand has been selected to be placed between its neighbor on each side, and there should be no noticeable difference between pearls that are side-by-side.