1. Luster
Image of Pearl Luster


A pearl's luster is a measure of its brilliance and reflectivity. High-quality pearls are bright and shiny -- you should be able to see your reflection in them. The appealing, deep shine of a pearl is often what defines its beauty. This is produced by multiple layers of semi-opaque calcium carbonate crystals, called nacre. The nacre reflects light on the surface of the pearl, producing brilliance and sheen. Luster is an integral feature in determining the quality of a pearl. Large pearls have a thicker nacre and, therefore, a higher luster.

2. Shape
Image of Pearl Shape


The shape of the pearl is one important area where "value" and personal taste may diverge. Perfectly round pearls are extremely rare, and therefore very expensive. However, pearls come in a wide variety of interesting and unique shapes, and you may find some of these shapes even more appropriate to your own taste and personality. Button pearls are slightly flattened into a disk-like "button" shape; drop pearls are teardrop-shaped; ringed pearls exhibit a series of concentric indentations or rings; and baroque pearls are abstract and asymmetrical. Many high-quality pearls can be found in these alternate shapes -- often at lower prices than a perfectly round pearl of the same quality -- and you may find the unique shape to be even more personally appealing and satisfying.

3. Size
Illustration of Pearl Size

An oyster's particular type and size has a direct effect on how large the pearl it produces will be, and pearls do come in a wide range of sizes. Round pearls are measured according to their diameter, while baroque pearls are measured by their length and width. A pearl's size does not necessarily affect its quality, but it does affect its price. Large, round pearls are rare and their luster is usually high. This beautiful combination of traits is often reflected in the cost of such pearls. Average pearl sizes (in diameter): Akoya: 6-8mm, freshwater: 5-6.5mm, South Sea: 11-13mm, Tahitian: 11-12mm.

4. Surface Markings and Blemishes
Image of Surface Markings and Blemishes

Often when an oyster creates a pearl, the nacre does not develop smoothly. The surface of a pearl is judged by how many marks are visible in the nacre. These imperfections can be small and unnoticeable or quite large and distinct. Like diamonds, pearls are rarely flawless. However, high luster or the way pearls are strung and set can help conceal surface markings.