Pearl Types
There are three broad types of pearls; natural pearls, salt water pearls and fresh water pearls. Both salt water and fresh water pearls are considered cultured pearls. Cultured pearls are still real pearls that are grown organically inside of oysters in the same way as natural pearls. The difference is that in the case of cultured pearls, the pearl farmer intentionally stimulates the development of the pearl by inserting a “nucleus” into the oyster. Below is some information and further discussions within each pearl type.

Natural Pearls
Natural pearls are formed randomly and are really simple accidents of nature. When an irritant, such as a parasite, (contrary to popular belief, sand is not the irritant) becomes lodged in the tissue of an oyster or other mollusk, the animal responds by secreting a calcium carbonate substance called nacre to coat the intruder as protection. Over a period of several years, this build-up of nacre forms a natural pearl. Natural pearls of any commercial value or desirability are extremely rare. Although natural pearls are found primarily in older jewelry from estate sales and auctions, their popularity is making a comeback. They are used mostly as individual centerpieces in unique jewelry designs. You will never find a matched multi-pearl necklace unless you are willing to pay the price. In 2007, a double strand of 68 matched natural pearls, known as the “Baroda Pearls”, was auctioned at Christie’s for $7 million.

Salt Water Pearls
Any pearls cultured in mollusks inhabiting salt waters are considered salt water pearls. The three most common types of salt water pearls are Akoya pearls, Tahitian pearls, and South Sea pearls.

Akoya Pearls: Akoya pearls are primarily grown in the cool to temperate salt water of Japan and China. This temperature allows the pearl to develop highly uniform mineral crystals resulting in brilliant luster. Thus, many experts believe Akoya pearls have the highest luster of all types which is a major factor in determining the value of pearls. Their size can range from 2 to 10 millimeters with the average size being 6-7mm. It normally takes about one year for a pearl to grow to an average harvestable size but this time can vary from between 8 and 24 months. Akoya pearls natural colors are pastel shades of rose, silver/white, cream, gold and grey/blue.

Tahitian Pearls: Tahitian pearls are found throughout the waters of French Polynesia. The limited area for Tahitian pearl cultivation is due to the area of optimum habitat of the mollusk that produces these prized pearls – the Black Lipped Oyster. Only about 1 in 10,000 of these oysters produces a pearl which makes mass cultivation impossible. It takes 22 to 26 months for a pearl to grow to the normal size range of from 8 – 18 millimeters. The average size is generally 9-10mm. Tahitian natural pearl colors include peacock (the most popular), black, dark grey, silver/grey, black/rose, black/blue, black/green and deep purple.

South Sea Pearls: South Sea pearls are grown in the warm waters off of Australia, Indonesia, the Philippines, and Thailand. These pearls and the oysters that contain them are the largest and rarest grown. It takes 20 to 24 months to grow the pearl. They are very rare due to many difficulties in cultivation. South Sea pearl size ranges from 9 – 20 millimeters with the average size around 13mm. South Sea pearls natural colors include silver, silver/pink, white, white/pink, white/gold and gold.

Fresh Water Pearls
Freshwater pearls are cultivated in lakes, rivers, ponds and other fresh water bodies. The largest numbers of fresh water pearls are produced in mainland China. Japan and even the USA also have limited fresh water pearl production. The cultivation process is a little different for fresh water pearls from their salt water pearl counterparts. A fresh water pearl is a cultured pearl where the mollusk was nucleated with a piece of mantle tissue in their mantle tissue. In all pearls cultured in salt water, the mollusk is nucleated in their reproductive organ with a piece of mantle tissue and a mother-of-pearl bead. In the past, fresh water pearls were primarily low quality irregular shaped pearls. Today, science has greatly improved the cultivation techniques resulting in higher quality freshwater pearls that are very round and very difficult to distinguish from the more expensive salt water Akoyas. There are also techniques to produce odd shaped fresh water pearls that are square, oval, or even heart-shaped. It takes 3 to 7 years for the fresh water pearls to grow and their size ranges from 3 – 13 millimeters with an average size of about 6mm. Even though the growth time is longer than that other more expensive pearls, fresh water pearls are much easier to cultivate and many times one oyster can produce up to 40 individual pearls at each harvest. Freshwater pearls come in a variety of pastel shades including white, pink, peach, lavender, grey, yellow and cream.