Pearl Grading Factors
Luster is the deep inner glow of the pearl and its brilliance to the human eye. For cultured pearl experts, this factor is perhaps the most important indicator in evaluating cultured pearl quality because it is what separates the ordinary from the extraordinary. Throughout history, this unique quality has separated pearls from all other gems and it is what many experts term the heart and soul of a pearl.
Surface quality refers specifically to the abundance or absence of physical blemishes. When evaluating surface (the trade uses such terms as blemish, spotting and cleanliness), remember that cultured pearls are grown by live oysters in nature. As such, there are many uncontrollable forces that affect the surface. The fewer the natural markings or spots on the pearl’s visible surface, the more expensive the pearl.
Shapes range in descending order of value from round to semi-round, from off-round to oval and from drop to baroque. Generally the shapes from round to drop are pretty symmetrical, while anything baroque denotes a pearl that is completely asymmetrical or free-form. The more spherical (rounder) and symmetrical the pearl, the more valuable it will be. Irregular shaped pearls can be very attractive and are usually less expensive than round pearls.
Cultured pearls come in a variety of colours from silvery white to black, with a rainbow of colours in between. This includes body colours (the overall colour) and overtones (translucent colours that appear over the body colour). Colour is entirely a matter of personal preference. Because of changes in the natural habitat, the availability of certain colours can vary – and scarcity affects price.
Pearls are measured by their diameter in millimeters. They can be smaller than one millimeter in the case of tiny seed pearls, or as large as twenty millimeters for a big South Sea pearl. The larger the pearl, other factors being equal, the more valuable it will be. Although this does depend on the type of pearl, for example if an extremely large Akoya pearl is discovered it may be more valuable than an average sized South Sea pearl.
Matching refers to pairs or strands, and addresses uniformity of colour, luster, shape, spotting and graduation. The more uniform and aesthetically pleasing two or more pearls look together the more time was spent matching the pearls. This time to match pearls is reflected in the cost. If colours are intentionally mixed, it refers to the attractiveness of the combination. Each pearl in a strand has been selected to be placed between its neighbors on each side, and there should be no noticeable difference between pearls that are side-by-side.