Pearl is the hard calcium carbonate substance which is produced from the oyster. The perfect pearl is the round and smooth pearl but it is hard to find in the natural. So the price of the ideal pearl is too expensive.
There are the 2 major type of pearl source. But they may sometimes look quite the same and difficult to explain the source.
1. Salt Water Pearl; The most popular pearl source in the world.
2. Freshwater Pearl
Freshwater pearl shell is a kind of bipolar oyster, which has big shape, thick layer and beauty nacreous layer inside. There are many usages of the pearl shell such as home furniture decoration, accessories and bags. Moreover, Pearl shells are used in cosmetic and medicine industries.
In Thailand, the specie of pearl shell; Chamberlainia hainesiana have been exported to Japan for breeding industries more than 25 years. There are 2 species of pearl shells in Thailand (Kanjanaburi): C. hainesiana and Hyriopsis (Limnoscapha myeriana). In the year of 1994, the specie of C. hainesiana could breed and abandon to the natural for the good ecology. It found that both types of pearl shells habit in only the river. Sometime you will see the freshwater pearl mussels are living in lakes and ponds.
Biology of pearl shell
1. Life cycle
The life cycle of pearl shell is similar to other bipolar oyster. There are two sexes of the shells. In the season of breeding, the females will receive the germ from the male shell to inhalant siphon and store in marsupial. After that it will fertile and develop to glochidia and juvenile and free living form at the last cycle.
2. The maturity
The maturity of H. (L.) Myeriana will have 7.92 centimeters long of shell, 26 grams weight. The maturity of C. hainesiana at the age of 2 years have 15.12 centimeters long of shell and 390 grams weight.
3. The season of fertility
It was reported that the fertility season begin from September to March. The duration from marsupial to free living form take 6 – 10 days up to the environment temperature. In one year, the shell C. Hainesiana can make marsupial average 10.50 times but H. (L.) myeriana can make marsupial average 18.92 times per year.
4. Host of the pearl shells
Both species of pearl shells in the stage of glochidia as host and develop to juvenile. One fish can be host of only glochidia because of the limitation of serum glucose of the fish.
The Freshwater Pearl in Thailand
Pearl compose of Calcium Carbonate (CaCO3) (aragonite 82 – 86 %), conchiolin 10 – 14 % and water 2 – 4 %. The hardness is 3.5 – 4.5 %. The specific gravity is 2.7.
Type of pearl: There are 2 types of pearls
1. Natural Pearl
The natural pearls cause from the foreign substance in natural contaminate in layer and nacreous layer of the shell.
2. Culture Pearl
The culture pearl causes from the human put some material into the shell and wait until the suitable size. There are 2 kinds of culture pearls
2.1 Hemispherical pearl or Half pearl
2.2 Spherical pearl
– Non-nucleated pearl; with this process will get irregular shape of pearl
– Nucleated pearl; by this process, the supplier will get cycle pearl, beauty layer and high value.