Pearl Grading takes into account shape, lustre, surface quality, nacre thickness and matching on the strand. Grading a strand of pearls like a necklace is slightly different to grading individual pearls as not every pearl on the strand will necessarily meet all the criteria for that grade.
Shape: pearls develop into a variety of shapes. Round pearls are the rarest and command the highest prices. The term ’round’ does not mean spherical like a marble but the pearls should not be obviously oval or flattened to the naked eye.
Lustre is the shine that gives pearls their beauty and is an important buying factor. Lustre refers to the pearls brilliance – the way it’s surface reflects light, and to it’s inner glow – how it refracts light from the layers of nacre within.
Pearls with low lustre appear chalky, yellow or dull rather than shiny. This example gives an idea of the lustre expected from different grades.
Surface Quality: pearls are a natural product and, like handblown glassware, small natural imperfections are quite acceptable. Unacceptable faults include cracks or holes in the surface or thin and flaking nacre.