The value for Tahitian Black Pearls is evaluated based on rarity and perfection. Each pearl is graded individually. Several criteria are used to evaluate each one. They are: Luster, Size, Shape, Orient, Color, and Surface.
Always look for luster first when selecting a Tahitian black pearl. The luster or reflective surface shine is the highly mirror-like quality. The better the luster the higher the quality pearl, because the luster indicates a thick layering of pearl material or nacre. Usually this means the pearl has been in the oyster a long time. The thicker the pearl nacre, the better the pearl.
Size is one of the most important criteria for evaluating black pearls. Since the Black Lipped Oyster is one of the largest oysters in the world, the pearls can also be of exceptional size. The size may average 8-10.5mm, or in some cases 11-14mm. The size is affected by the nucleus and the nacreous layer secreted around it, as well as the size and health of the oyster. Size is only one of the factors used to grade black pearls. Each pearl is evaluated individually using all six criteria.
Tahitian black pearls come in a wide range of natural shapes ranging from pear-shaped, tear-drop, button, mushroom, acorn, barrel, and baroque shapes. All the shapes of black pearls are considered desirable and marketable. Often, the pear-shaped and baroque pearls are set in pendant designs, and the rounder pearls are used for and . Round pearls are harder for the oyster to create and therefore they are more rare and more expensive.
The orient is the heart and soul of the pearl. The orient is defined as the way the pearl reflects and decomposes light through aragonite crystals. The orient is the play of light penetrating the surface, the depth of color and light that can be observed by looking past the reflective lustrous surface and into the many layers of pearl material or nacre. Each layer reflects light and creates the illuminating glow reflecting light from within the pearl. The best way to observe orient is to hold the pearl in front of a neutral background such as a white shell. As light shines into the pearl, the eye is able to see past the surface color and to the colors of each layer of nacre that surrounds the pearl.
Tahitian black pearls come in a rainbow of beautiful natural colors. Each color is special, and each is sought after by collectors. The most important factor in selecting color is to determine which color looks best on the wearer. The colors comes alive on different skin tones and complexions. All pearls have an under-color ranging from pale silver to dark black. Often, there will also be a layering of iridescent hues in addition to the under color. These shimmering colors can be peach, copper, grey, pink, sea green, turquoise blue, peacock green, burgundy and bordeaux, indigo and navy, purple and lavender to canary and cranberry to deep midnight black.
The outer skin of the pearl may be analyzed for smoothness and perfection to determine the "beauty-marks" or imperfections of the pearl. Every pearl will have some tiny "surface marks" which add to the character and personality of each pearl. Most birthmarks are imperceptible to the naked eye and give the pearl character. The beauty marks help to determine if the pearl is "real", i.e. a natural color natural shape cultured gem. Simulated pearls, faux pearls and beads will have a perfectly smooth surface.