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Types of pearls

Freshwater Pearls

Freshwater Pearls come from Molluscs that for simplicity sake we call 'Mussels' whereas Saltwater Pearls are produced from Oysters. there are two families of mussels that produce freshwater pearls regularly, they are Margaritiferidae and Unionidae. Margaritiferidae is widely distributed in the Northern latitudes and would include areas such as Northern Europe, Japan and Northern America. However most of our freshwater pearls come from the Unioidae family, particularly the Genus Hyriopsis.

Freshwater Mussel - Hyriopsis cumingii

Freshwater Mussel - Hyriopsis cumingii

Freshwater pearls are particularly known for their wide range of whimsical shapes and colours, they are plentiful and an affordable alternative to their more expensive saltwater cousins. However, the closer to round and large, the higher the price comparing well with Akoya pearls. Freshwater pearls can come from anywhere there is a supply of fresh water, but in practice the major fresh water farms are in China on the Yangtze River Delta. In China the most prevalent mussel that produces cultivated pearls is Hyriopsis cumingii that produces a variety of coloured pearls, and Cristaria plicata that produces mainly white, cream and some pink pearls. In Japan on Lake Biwa and to a lesser degree, Lake Kasumigaura, have developed many varieties with doubtful sucess rates and the main production comes from the Hyriopsis schlegelii. Freshwater pearls are found in many other parts of the world, particularly from the United States of America around the Mississippi River Basin.

Saltwater Pearls

Akoya Pearls

Japanese Akoya Pearl Oyster - Pinctada martensii

Japanese Akoya Pearl Oyster - Pinctada martensii

Akoya pearls were historically the name given to Japanese Pearls and much valued for their high quality, as immortalized by "Mikimoto". Today most of the cultured pearl production in Japan comes from the Mollusc Pinctada Martensii a particularly hardy Pinctada capable of withstanding strong temperature changes.

Chinese Akoya Pearl Oyster - Pinctada chemnitzii

The Pinctada Chemnitzii favours waters from the Kyushu Islands south to the China Sea and produces what is popularly called a Chinese Akoya Cultured Pearl or just Chinese Akoya. The Akoya is generally a smaller pearl of approximately 7-8mm in diameter and are brilliantly white in the main but may come in a rainbow of other colours.

South Seas Pearls - Silver-Lip oyster & Gold-Lip oyster

Gold Lip Pearl Oyster Pinctada Maxima

Pinctada Maxima - Gold Lip Oyster with 2 Blister Pearls

The majority of South Seas Pearls come from the large but difficult to cultivate Pinctada Maxima which suffers high mortality rates, The successful ones can produce beautiful pearls of between 8mm and 20mm, with 13mm being the average. Only 10 to30% of the harvest will produce round (or near round) pearls, the rest being baroque and drop shaped, are still highly valued because of their beauty and relative rarity. The White South Seas Pearls come mainly from Australia. Other centres are Indonesia and the Phillipines. 

Tahitian Pearls - Black-Lip oyster - Pinctada margaritifera

Pinctada margaritifera - Tahitian Black Lip Pearl Oyster

Tahitian Pearls are so named because they are found mainly in the French Polynesian Islands. The Tahitian black lipped oyster produces a stunning array of iridescent black, grey, and greenish black saltwater pearls. The cultivation and export of true Tahitian pearls are government controlled to ensure consistent quality and minimum standards. Only about 5-10% of pearls produced are round and therefore command high prices but all the other shapes are available and much sought after. The thick nacre of at least 0.8mm ensures high lustre and vivid colours. AAA grade Tahitian pearls are very high lustre and have a clean surface (one to a few slight flaws are distributed over less than 10% of the pearl surface).

Keshi Cultured Pearls & Seed Pearls

The term "Keshi", "Seed" or sometimes "Bead" Pearl, is used to describe a Natural pearl (one that is formed in the wild by nature with no interference from man) this is not the case. “Keshi” is the Japanese word given to very small things and the word has become, through popular usage, used to refer to small pearls produced without nucleation. Therefore, the term for a pearl without a nucleus but produced by a “farmed” or “worked” pearl mollusc, is a “Keshi Cultured Pearl” or “Cultured Keshi Pearl”.

The formation of a Keshi Cultured Pearl (seed pearl) is the result of one of the following:

  • Firstly, the mollusc rejects the nucleus placed there in the grafting process thus the mantle tissue (epithelium) remains and the nacre forms around this tissue to produce a “Keshi” pearl, just as would happen in the wild with a natural pearl.
  • The second cause; may be that the mollusc’s mantle was damaged during the implanting operation through inexperienced handling causing epithelium cells to be lodged in mantle tissue and this may create a pearl sack that in turn may produce a Keshi pearl. (If this injury was to happen in the wild from say a fish bite, then the pearl produced would be a Natural pearl, due to the absence of man’s intervention.)
  • The third possibility; is that epithelium cells of the mantle tissue are grafted into the body of the mollusc on purpose, to create a Keshi pearl, that is without the inclusion of a nucleus.
  • There is another type of so called “Keshi” that is appearing and that is a Keshi pearl and a nucleus that have been implanted into a pearl sack to fuse together and form a new baroque shape. These are not Keshi pearls.
  • There are both Saltwater and Freshwater Cultured Keshi Pearls. As the mollusc does not know the difference between a nucleated implant and a non nucleated implant the resulting pearls will share the same characteristics in colours and properties, although it is rare to find a round Keshi due to the randomness of its original form. Also, the size of Keshi are a lot smaller as a rule due to the absence of a nucleus.