The most frequent question my clients ask me is how they should choose their pearls? The simplest answer I can give them is to choose pearls they love. There are, however, technical answers to this question. The Gemological Institute of America (GIA) provides a set of seven value factors for grading pearls. These are: Size, Color, Shape, Luster, Nacre Quality, Surface Quality, and Matching (within a strand or set). In general, pearls of higher luster will provide higher value (in the long run) over pearl size, shape and color. This article talks about Pearl Luster value factor.

Luster actually comes from within the pearl surface. No other gemstone shares this characteristic. Other gemstones, diamonds, rubies and sapphires, shine from the surface. Pearls get their luster from the light reflecting off the aragonite (a form of calcium-carbonate) crystals that form the nacre (pronounced NAY-ker), or skin, of the pearl. Thus, the incomparable glow that comes from pearls.

Different varieties of pearls exhibit different qualities of luster. Akoya cultured pearls are renown for their high luster. The colder waters of Japan, where Akoyas are grown, are believed to produce long, thin aragonite crystals which thus reflect the light differently than Tahitians and South Seas. I have seen Akoyas that look like glass when viewed in the bright sunlight