The pearl is one of the few organic gems, meaning it forms through the activity of a plant or animal. The ancients had many theories about its origins, calling it a "gallstone trapped within a mollusk" or a "hardened oyster egg." Today we know that it takes a certain type of mollusk to make a pearl. These varieties, certain oysters, mussels and clams, must be able to produce an iridescent, mother-of-pearl lining within their shells. Natural pearl growth occurs when a mollusk protects itself from an irritation. The irritant may be a small animal, but rarely is it a grain of sand. The layers of protection form what is called nacre, which is what gives a pearl its subtle beauty. Cultured pearls form in basically the same way, except that humans create the irritation by placing an object into the animal. Growth time for most saltwater cultured pearls is between six months and two years. Freshwater cultured pearls take anywhere between two and six years to grow. Today we enjoy a large range of cultured pearls. There are the akoya, or saltwater pearls from Japan and China. These pearls can reach up to about 1Omm. For those wanting a bigger pearl, there are the cultured pearls from the South Seas and Tahiti, which can reach sizes of 17mm to18mm. And then there are cultured freshwater pearls that range in size from 2mm to 11mm. Most freshwater cultured pearls are grown in Chinese waters. With the exception of South Sea and Tahitian pearls, most cultured pearls are bleached to help even out their color. Other pearl treatments include dyeing and irradiation.

    Seven value factors are applied to pearls.

  1. Size. Pearl size is measured in millimeters, all other factors being equal, a larger pearl of a certain type is more expensive than a smaller one.
  2. Shape. There are three main categories:
  1. Spherical (Round),
  2. Symmetrical (such as Oval) and
  3. Baroque (Irregular).

Generally, round pearls will be the most expensive.

  1. Color. Two sub categories are body color and, if present, overtone. Body color is the dominant color of the pearl, while overtone refers to one or more translucent colors that overlie the body color (like blush on a woman's cheeks). A third component of some pearls' color is orient. When present it looks like iridescence just below a pearl's surface.
  2. Luster. This is the intensity of light reflected from a pearl's surface. In general, the more lustrous pearls will have a higher value. The G.I.A. uses the terms excellent, good, fair and poor to describe luster.
  3. Surface Quality. This factor looks at the blemishes, or surface irregularities. Typical blemishes include bumps, abrasions and spots. Most cultured pearls are not completely blemish-free, but the visibility of the irregularities will affect the price.
  4. Nacre Quality. Good quality means that it has a reasonable thickness of nacre and the pearl itself does not have a chalky appearance.
  5. Matching. This is the uniformity in the strand of pearls and multi-pearl pieces of jewelry, and is judged by the consistency of all the above factors.

The image on the left shows a certification for a natural pearl.  This pearl is not cultured, which means an object like a grain of sand began the process.  Non-cultured, or natural pearls, take much longer to form than a cultured pearl.  The cultured pearl may have a 5mm bead placed in the mollusk and after a period of time, a 6mm pearl is grown.  This means that only a 1 mm layer of actual pearl material covers a cultured pearl, saving the pearl farmer time and saving you money.