Pearl Grading

The quality of a pearl is based on five main criteria.  Based on these five determinants, pearls are then graded into categories such as: A, B, C, and so on.  On average only about 5-10% of harvested pearls will be classified as grade A.

Luster

A pearl’s luster is determined by its nacre, the hardened substance that the oyster secretes to coat the nucleus.  A pearl with excellent luster will have a thick amount of nacre giving it a lustrous, milky quality. Pearls with high quality luster will also have brilliant orient, or iridescence, which is due to fine quality nacre and cannot be replicated.  This is the single quality that places saltwater pearls on a superior level to freshwater pearls.


Cleanliness

A clean pearl without imperfections on its surface is graded higher than a pearl with spotted blemishes.  Some pearls may have minor spots where the nacre hasn’t formed smoothly over the pearl.
 


Shape

Round pearls are the epitome of a perfect pearl, however, pearls also come in a variety of naturally forming shapes, including off-round, drop-shaped, button-shaped, baroque, semi-baroque, and circlé.  Because round pearls are valued for their perfect symmetry, they are generally graded higher than other shapes.


Color

The color of a pearl is determined by genetics.  The range of colors found in the mother-of-pearl inside the oyster shell will be the range of colors passed on to the pearl.

While there are different grading systems pertaining to color for South Sea, Tahitian, and Akoya pearls, generally the brighter and rarer a pearl’s hue, the higher it will be graded.  For example, with South Sea pearls, a premium is placed on pearls that are white, rather than creamy or silvery.  With South Sea pearls that are golden, those that have a deep golden color are valued more than the fainter yellow color. And with Tahitian pearls, the extraordinary colors of peacock green, pistachio, and aubergine are graded higher.


Size

Because large pearls are rare, any pearl in excess of 15mm is treasured and commands a high price.  Generally the larger the size of the pearl, the more it is appreciated.   In general, a 1mm increase in the size of medium quality pearls can raise their price by 100-200%.  For example, a 14mm pearl which costs $5,000 would cost $10,000 if it were 15mm and $30,000 if it were 16mm.
 
To find 50 perfectly matched high-quality pearls for a 16-inch necklace, nearly 10,000 pearls will need to be sorted through to match for color, shape, luster and cleanliness.