Pearls are graded according to several characteristics - lustre, shape, color, surface, size, nacre quality, and matching. A Pearl's worth depends on the combination of these seven value factors. Below is a brief introduction of how to grade pearls.
Lustre
Luster is the surface brilliancy of pearls. It is probably the best expression of a pearl's beauty.
Low lustre pearls appear milky or chalky.
High lustre pearls reflect light well and show mirror-like reflections.
Lustre depends a great deal on the quality of care bestowed on the product in its early growing stages. The better the pearl producer cares for his molluscs, the better the pearl.
As with natural pearls, high quality lustrous pearls make up only a fraction of the pearls available on the market, and command the very highest prices.
Since a very lustrous baroque pearl is probably more desirable than a round milky pearl, lustre is generally considered to be one of the most important aspects of a pearl’s grading and valuation.
Shape
Pearls are graded by shape into four levels: Semi-baroque and baroque, Off round, Slightly off round, and Round.
Round is generally the most expensive variety. A proper round pearl is symmetrical and will roll in a straight line. Again, only a small percentage of total pearl production will give you true round pearls.
There are various terms are used as indications that the pearls are ‘roundish’ in various degrees.
Color
Pearls come in a wide range of natural colors/shades. It is a combination of body color and overtone. Body color is the predominant basic color of the pearl. When pearls lay on a white surface, body color can be best seen on the outer edge of the pearl. Body colors include white, light pink or pink, light cream, and dark cream, yellow or golden. Overtone is one or two colors that overlie the body color. When inspecting pearls under light, you may see color in the central dark areas of the pearls. This is the overtone. Overtone colors include pink, silver, and green.
Color is a matter of personal taste and is often selected on the grounds of whether it suits the wearer’s skin tone or not.
Surface
All the factors that disturb the surface smoothness of the pearl and hence decide its appearance are called blemishes and imperfections (also called spots or flaws).
The fewer blemishes a pearl has, the more valuable it is. Blemishes are marks, bumps or little pot holes which, in reality, give each strand its unique identifying factors.
To find pearls without blemishes is rare and their price is likely to be astronomical, given other quality factors being high. One has to remember, pearls are organically grown and just like the human body, no two are exactly alike.
When assessing pearls, always look at each pearl individually and carefully to judge the surface quality.
Size
Size means the pearl's diameter measurement. Pearl size is expressed in millimeters, rounded to the nearest 0.5MM.
The larger the pearl, the more valuable it is.
Each of the main types of pearls has a common range of sizes:
Freshwater pearls typically range from 3mm up to 12mm,
South Sea or Tahitian Pearls start from around 8mm right up to 18mm or larger.
Akoya pearls average 4mm to 10mm.
Nacre
Nacre is the coating that the oyster forms around the nucleus of the pearl. Nacre thickness is more than the amount of nacre. It has other meaningful aspects as well. The structure of the nacre is composed of thousands of layers of thin calcium carbonate crystals. This distinctive nacre structure influences the color, luster, durability and elasticity of the pearl.
Pearls with very thin nacre allow the core nuclei to be seen through the nacre. Pearls with very thin nacre often exhibit visible cracks in the nacre. Pearls with very thin nacre can also display signs of nacre peeling or chipping.
Matching
Matching refers to all previously discussed factors: size, color, shape, luster, nacre and surface quality. Matching applies to pair of pearls and strand of pearls.
