Pearls are created by nature; therefore, there are various sizes, shapes and types of pearls. The majority of pearls are cultured and formed in the oyster. The cultured pearl is formed from a foreign substance that has been inserted in the oyster. The oyster secretes a material called nacre in order to protect itself against the irritant. The nacre develops around the irritant which then develops into a cultured pearl.
There are two categories of cultured pearls which are Saltwater and Freshwater. Within these categories are various types of pearls from different regions. Temperature and type of water also determine what an oyster will produce.
Types of Pearls:
Japanese Akoya Pearls – These are the most common type of cultured pearls. Japanese Akoya pearls are cultivated mostly in Ago Bay in Japan. They tend to be more expensive than some other pearls because of the production of a single pearl or no pearl in an oyster. These pearls can range from 2.0mm to 10.0mm.
Tahitian Pearls - Cultivated in Tahiti in the Black Lip Oyster. These pearls are natural in color and can range from 8.0mm and can go as big as 18.0mm. Their color can range from silvery grey to deep peacock black.
South Sea Pearls – This also includes Golden South Sea Pearls. These are cultivated in warmer waters around Australia and the Philippines. Because of the nature of the oyster, South Sea pearls tend to be larger in size. These can range from 8.0mm to 18.0mm.
Keshi Pearls – These are formed by natural means, without implantation. Sizes can vary from 1-2mm in the Akoya Oyster to larger than 9mm in South Sea Keshi.
Mabe Pearls – These pearls are formed against the inside of the mollusk which gives them a unique half-dome shape. Sizes, shapes and colors vary.
Biwa Pearls – Japanese Freshwater Pearls are found only in Lake Biwa in Japan. However, as of now the Lake is contaminated, so the production of this pearl has stopped.
Freshwater Pearls – These pearls are mostly cultured in lakes or rivers in China. Freshwater pearls can range in size, shape and color.
Basic Pearl Terms:
Nacre - The substance which the oyster secretes to form pearls.
Nucleus – The stimulant placed in a pearl oyster, around which the oyster deposits nacre to form a pearl.
Luster – The true glow of the pearl permeating from within.
Millimeter – The diameter measurements of the pearl. Approximately 1/25th of an inch.
Momme – Japanese weight measurements used for pearls. One momme is quivalent to 3.75 grams, or 18.75 carats.
Baroque – Off-shape; not round.
Uniform – A necklace with nearly equal-sized pearls throughout.
Graduated – A necklace in which pearls gradually increase in size.
Choker – A necklace that is approximately 15" - 16" in length.
Princess – A necklace that is approximately 18" in length.
Matinee – A necklace that is approximately 20" - 24" in length.
Opera – A necklace that is approximately 28" - 30" in length.
Bib – A necklace of three or more strands.
Rope – A necklace of 45" or more in length. Also called sautoir or lariat.