Pearl Grading & Information

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 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, would 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:

• Akoya cultured - 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 muscles, 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 Grading Defined & Explained

Pearl Grading is the practice of assigning degrees of quality to a pearl or a piece of pearl jewelry based of the quality attributes designated by industry best practices and authority groups such as GIA and EGL.

Currently there is not one single standard pearl grading system that is agreed on and used industry-wide. As with any item that is available in a wide variety of shapes, sizes, colors and conditions, a standardized system of grading must be used when purchasing or selling pearls. Only with a grading system can the pearl be described according to mutually agreed-upon and understood terms so that both buyer and seller can determine a fair price. Unfortunately, the pearl industry as a whole has not adopted a universally used standard grading system. Instead, the specific grading system often used, depends upon the specific jeweler or pearl distributor. Eventually a standard system will come into the market - most likely developed by the Gemological Institute of America. Until that time, those in the industry must rely on commonly accepted grading systems derived from the quality grading characteristics of pearls.

There Are Two Major Pearl Grading Systems
There are two major pearl grading systems in fairly widespread use: the AAA-A system and the A-D system (also called the Tahitian system). These are the most accepted systems, and considered standard by nearly all reputable pearl dealers, both retail and wholesale.

The AAA-A System
This system grades pearls on a scale from AAA to A, with AAA being the highest grade. This grading scale is common to freshwater and akoya pearls only, but is accepted by many with South Sea and Tahitian pearls as well:

• AAA:The highest-quality pearl, virtually flawless. The surface will have a very high luster, and at least 95% of the surface will be free from any type of defect.
• AA: The surface will have a very high luster, and at least 75% of the surface will be free from any type of defect.
• A: This is the lowest jewelry-grade pearl, with a lower luster and/or more than 25% of the surface showing defects. In many cases, if the pearl is being mounted into a piece of jewelry, it can be mounted so that the defects are hidden -- thus providing a lovely jewelry piece at a lower price.

Intermediate Grades And Pearl Grading For Stands
Some reputable sellers may also use intermediate grades for the pearls - those pearls that do not fall in a category but are between two - such as A+ and AA+. Obviously, these grading categories are quite broad and leave room for interpretation and individual judgment. Also note that in multi-pearl pieces such as strands, necklaces, bracelets, etc., every one of the individual pearls may not absolutely meet the indicated grade level. For example, a strand referred to as "AAA" must have most of its pearls as AAA pearls. However, a few pearls could have slightly lower luster or a tiny bit more surface defects. This is because matching is also a primary consideration in multi-pearl jewelry, sometimes even overriding a very strict grading of each individual pearl.

The A-D System (or Tahitian System)
This system grades pearls on a scale from A to D, with A being the highest grade. This is the system used in French Polynesia (based on a government standard there) to grade Tahitian pearls, and South Sea pearls only. It is therefore sometimes referred to as the "Tahitian system." While this system is standard in producing countries, other markets will still utilize AAA-A. It is important to note that the following grading system can be interchanged with the AAA-A system.

• A: The highest-quality pearl, with very high luster and only minor imperfections over less than 10% of its surface.
• B: High or medium luster. Surface may have some visible imperfections, but over no more than 30% of its area.
• C: Medium luster with surface defects over not more than 60% of the surface area.
• D: May have many slight defects, but no deep ones, spread over 60% of its surface; or deep defects over no more than 60% of its surface; or a combination of minor and deep defects over no more than 60% of its surface. In this grade of pearl, the luster is irrelevant. Even the most  lustrous pearls will be graded D if their surface is blemished to this extent. Pearls below D grade are considered not acceptable for use in jewelry.

Nacre Is The Final Factor In Grading Pearls Both of the grading systems described above focus primarily on the luster and surface quality of the pearl to determine its grade. But keep in mind that other factors also contribute to the quality and final grade of any pearl. One of the most important is the thickness of the nacre, which often determines how durable the pearl will be over time. The thicker the nacre, the stronger and longer-lasting the pearl (provided it is treated well, of course!) For Tahitian pearls, the government of French Polynesia has set a minimum nacre thickness of 0.8 millimeters. Any pearls with nacre of less than that thickness are not allowed to be sold. Keeping in mind that Tahitian pearls tend to be larger than many other pearls (such as akoyas), you can use this rule as a guideline when evaluating your own potential pearl purchases.