Pearl Quality & Value Factors
Pearls are unique products of nature, organic results of living creatures. There is no universal system for evaluating pearls like there is with diamonds, but by using these nuancing principles, we can consider each pearl and create beautiful jewellery.
Factors that determine quality, value & beauty of pearls:
Type of Pearl
Primarily important for evaluation is the identification of the Pearl type; freshwater, akoya, Tahitian or South Sea, as each has their own characteristics and trademarks. Each type of pearl is produced by a different species of mollusc (pearl oyster), and each mollusc lives in a different region of the world under very specific climatic conditions.
Lustre is the way the light plays off of the surface of the pearl, and is judged by it brilliance and ability to reflect light. Due to the pearls' nacre structure, light does not just reflect off of the surface of the pearl. Rather, light penetrates the surface and seems to reflect from WITHIN the pearl. The way that a pearl seems to emit light is its lustre. A pearl with a high lustre will be very shiny and show reflections while a pearl with poor lustre will appear milky or chalky. Only strong layers of nacre can produce deep lustre.
Lustre is determined by the quality of a pearl’s nacre; its transparency, smoothness and overall thickness are very important to the peals’ beauty and value. Factors affecting the quality of the nacre include the cultivation place, the health of the mother oyster, length of cultivation, environment and the type of oyster used.
A pearl with a high lustre will be very shiny and show reflections, while a pearl with poor lustre will appear very milky or chalky. Only strong layers of nacre can produce deep lustre.
Pearls present a whole palette of colours, some naturally occurring are white, champagne, aqua, green, golden, and black. Within each colour category, there are a number of common overtones, or subtle variations in the surface iridescence. Above all, a pearl’s colour is a question of personal taste. Some colours look better on certain skin tones.
Colour is a result of the breed of the host mollusc and that of the donor tissue, as well as a multiple of external influences, including diet, water temperature and environment.
Pearl colour is a combination of three elements:
- Body colours: Body colour is the dominant hue of a pearl. What colour do you see when you just glance at the pearl?
- Overtones: Translucent colour that overlies body colour. If you tilt the pearl from side to side and squint, is there a slight tinge of a secondary colour?
- Orient: Iridescent rainbow colours on the surface. This is the magical, rainbow wash you see when you look at a pearl.
All pearls have a body colour, but not every pearl displays overtone and/or orient.
Although some shades are especially rare or popular and therefore highly valued, such as rosy white, silvery white and pale gold, the colour of a pearl is not an indication of its quality.
Nacre is the natural substance that the mollusc secretes to protect its sensitive flesh from irritants such as shell fragments, parasites or implanted beads. This is the same beautiful iridescent material that lines the inner surface of the mollusc shells, aptly named mother of pearl. Nacre thickness is a quality characteristic only applied to saltwater, bead-nucleated pearls. It is not applied to keshi pearls or freshwater pearls as both are composed of solid nacre.
The only way to determine the exact thickness of the nacre is to x-ray the pearl or cut it in half (I don't recommend cutting your pearls in half!). However, there are ways that we can visually assess the nacre quality. With careful examination, the nacre thickness can at times be visible through the pearl’s drill hole. With thin nacre, it may be possible to see the bead nucleus through the surface, which will be very chalky or dull as a result, lacking lustre.
The longer the cultured pearl is allowed to remain in the oyster, the thicker the nacre coating will be. However, the longer the pearl remains in the oyster, the greater the chance of blemishes or misshapen pearls.
The pearl shape is the silhouette of the pearl, which ranges within three distinct shape categories: Spherical, Symmetrical, and Baroque. For any other shape, it is described as it appears (coin, stick, button, etc). Round is the most valuable and they decrease in value as they become less round. A baroque pearl is very irregular in shape with a surface that is often very uneven, however can just as well be very lustrous and appealing.
A pearl's shape is dependent on several factors:
- The shape of the bead nucleus
- Length of time the mollusc stays in water
- Climate and nutrient conditions of the growing environment
The longer the pearl remains within the mollusc, the greater the chance of developing an irregular shape. A perfectly round pearl is very rare. Even if the bead nucleus is round, the pearl may not grow evenly in all directions. A large, perfectly round pearl is even more rare.
The more flawless the surface of the pearl, the higher the value. However, since pearls are created in the ocean by a wild oyster and nature almost always leaves its mark, it is extremely rare to find a perfect pearl. Flaws can also be positive feature because they add character and prove that it is not imitation. Many people view these markings as unique and individualised characteristics.
Like other gemstones, pearls have clarity characteristics, but since pearls are not transparent or translucent, clarity is confined to the surface as blemishes in the surface complexion. Surface complexion is defined by the degree and visibility of surface imperfections. The fewer blemishes, the better the surface complexion.
Pearl blemishes that are seen include: Pits, Abrasions, Bumps, Ridges, Chips, Cracks, Flat areas, spots, or uneven nacre coating. Surface complexion is categorised using the terms: clean, lightly blemished, moderately blemished, heavily blemished.
A spotless pearl is extremely rare and valuable. If, for example, a pearl is large with excellent lustre, these qualities will outweigh minor surface imperfections. Large or numerous imperfections not only lower the value, but can affect durability and the ability to see a pearl’s lustre as well.
The size of the pearl is important because larger pearls, just like diamonds, are harder to find. Size will have a significant impact on the value. All other value factors being equal, a larger pearl will be more valuable. The size of a pearl is expressed in terms of its diameter, which is measured in millimetres. One millimetre increase in size is a jump in appearance and has been known to raise a price by up to 200%.
Pearl size is dependent on several factors:
- The mollusc species—some can grow larger pearl than others
- The size & health of the mollusc
- The size of the bead nucleus
- Length of time the mollusc stays underwater
- Climate and nutrient conditions of the growing environment