Pearls are unique and special gemstones that are created in an organic and natural way. Pearl quality can determine the overall value of a natural or cultured pearl or a piece of pearl jewellery: size, shape, colour, lustre, surface quality, nacre quality, and pearl matching within a jewellery piece. These factors indicate not just the quality of the pearl, but the value and beauty of it as well.
Size: Larger pearls are rarer and more valuable than smaller pearls of the same type.
Shape: Round is the most difficult shape to culture, making it the rarest cultured pearl shape and generally the most valuable. A well-formed pear, oval, or irregularly shaped cultured pearls are also prized by pearl lovers.
Colour: Natural and cultured pearls occur in a broad range of colours. Pearl colour can have three components. Bodycolour is the pearl’s dominant overall colour. Overtone is one or more translucent colours that lie over a pearl’s bodycolour. An orient is a shimmer of iridescent rainbow colours on or just below a pearl’s surface. All pearls display bodycolour, but only some show overtone, orient, or both. Warm hues include yellow, orange, and pink, and cool hues include blue, green, and violet. Pearls have a wide range of tone from light to dark. Pearl colours tend to be muted, with a soft, subtle quality.
Lustre: Of all the pearl quality factors, lustre might be the most important to high quality pearls. Lustre is what gives a natural or cultured pearl its unique beauty. Pearls with excellent lustre have reflections that are bright, sharp, and distinct. Pearls with good lustre have bright reflections, but the reflections are not sharp and look slightly hazy around the edges. Pearls with fair lustre have reflections that are weak, hazy, and blurred. Pearls with poor lustre have reflections that are dim and diffused.The higher the lustre, the more valuable the pearl.
Surface Quality: Like coloured stones, most pearls never achieve perfection. Some might show abrasions that look like a series of scratches on the surface, or a flattened section that doesn’t affect its basic shape, or an irregular ridge that looks like a crease or wrinkle. Look for an absence of disfiguring spots, bumps or cracks on the surface of a pearl, also known as “cleanliness.” The highest quality pearls have a sharp, mirror-like reflection.
Nacre Quality: Nacre thickness is a quality characteristic only applied to saltwater, bead-nucleated pearls and can be a clear indicator in pearl quality since lustre and nacre quality are closely related. If the nucleus is visible under the nacre, or if the pearl has a dull, chalky appearance, you can assume that the nacre is thin. This affects the lustre as well as the durability of the pearl.
Pearl Matching: Jewellery designers sometimes deliberately mix colours, shapes, and sizes for unique effects, but for most pearl strands, earrings, or other multiple-pearl jewellery, the pearls should match in all the quality factors. Colours, shapes and sizes should be comparable throughout the piece- especially on a high quality pearl necklace, bracelet or earring set.