"Wild pearl " or "natural pearl" is one that forms without any human intervention at all, in the wild, and is very rare. Many hundreds of pearl oysters or pearl mussels have to be gathered and opened, and thus killed, in order to find even one wild pearl, and for many centuries that was the only
way pearls were obtained. This was the main reason why pearls fetched such extraordinary prices in the past. A cultured pearl is formed in a pearl farm, using human intervention as well as natural processes.
One family of nacreous pearl bivalves – the pearl oyster – lives in the sea, while the other – a very different group of bivalves – lives in freshwater; these are the river mussels such as the freshwater pearl mussel. Saltwater pearls can grow in several species of marine pearl oysters in the family Pteriidae. Freshwater pearls grow within certain (but by no means all) species of freshwater mussels in the order Unionida, the families Unionidae and Margaritiferidae.
pearls, a perfectly natural
Diagram comparing a cross-section of a cultured pearl, upper, with a natural pearl, lower
The difference between wild and cultured pearls focuses on whether the pearl was created spontaneously by nature – without human intervention – or with human aid. Pearls are formed inside the shell of certain mollusks as a defense
mechanism against a potentially threatening irritant such as a parasite inside its shell, or an attack from outside, injuring the mantle tissue. The mollusk creates a pearl sac to seal off the irritation.
The mantle of the mollusk deposits layers of calcium carbonate (CaCO3) in the form of the mineral aragonite or a mixture of aragonite and calcite (polymorphs with the same chemical formula, but different crystal structures) held together by an organic horn-like compound called conchiolin. The combination of aragonite and conchiolin is called nacre, which makes up mother-of-pearl. The commonly held belief that a grain of sand acts as the irritant is in fact rarely the case. Typical stimuli include organic material, parasites, or even damage that displaces mantle
Pearl oyster
Pearl oysters are saltwater clams, marine bivalve molluscs in the family Pteriidae. They have a strong inner shell layer composed of nacre, also known as "mother of pearl".
Pearl oysters are not closely related to either the edible oysters of family Ostreidae, or the freshwater pearl mussels of the families Unionidae and Margaritiferidae.
Pinctada maxima pearl oysters are the only oyster that produces South Sea pearls. Currently they are cultured primarily in Australia and Tahiti.
All species within the genus share the ability to make pearls of commercial value. Attempts have been made to harvest pearls commercially from many Pinctada species. However, the only species that are currently of significant commercial interest are:
Gulf pearl oyster, Pinctada radiata; Persian Gulf, Red Sea, Mediterranean Sea and throughout the Indo-Pacific as far as Japan and Australia.
Black-lip oyster, Pinctada margaritifera; Persian Gulf and southwestern part of Indian Ocean; Fiji; Tahiti; Myanmar; Baja California; Gulf of Mexico
Gold-lip oyster, Pinctada maxima; Australia; Fiji; Tahiti;
White-lip oyster, Pinctada maxima; Australia; Fiji; Tahiti; Myanmar;
Akoya pearl oyster or Akoya pearl oyster, Pinctada fucata (also called P. imbricata), Red Sea; Sri Lanka; Persian Gulf; Indian Ocean; Western Pacific Ocean; Australia; China;
Shark Bay pearl oyster Pinctada albina; Australia
The various species of Pinctada produce different maximum sizes and colors of pearls, depending on the size of the species and the natural color of the nacre inside the shell. Black South Sea pearls, or Tahitian pearls come from the black-lip oyster; white and golden South Sea pearls from the white-lip and golden-lip oysters; and Akoya cultured pearls from Pinctada fucata martensii, the Akoya pearl oyster.
Diamond, Mining area
Today, most commercially viable diamond deposits are in Russia (mostly in Sakha Republic, for example Mir pipe and Udachnaya pipe), Botswana, Australia (Northern and Western Australia) and the Democratic Republic of Congo. In 2005, Russia produced almost one-fifth of the global diamond output, reports the British Geological Survey. Australia boasts the richest
diamantiferous pipe, with production from the Argyle diamond mine reaching peak levels of 42 metric tons per year in the 1990s. There are also commercial deposits being actively mined in the Northwest Territories of Canada and Brazil. Diamond prospectors continue to search the globe for diamond-bearing kimberlite and lamproite pipes.
Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care is required not to destroy larger diamonds, and then sorted by density. Today, diamonds are located in the diamond-rich
Diamond (gemstone)
The name diamond is derived from the ancient Greek . Diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could be found many centuries ago along the rivers Penner, Krishna and Godavari. Diamonds have been known in India for at least 3,000 years but most likely 6,000 years.
Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history. The popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns.
In 1772, Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen, and showed that the only product of the combustion was carbon dioxide, proving that diamond is composed of carbon. Later in 1797, Smithson Tennant repeated and expanded that experiment. By demonstrating that burning diamond and
graphite releases the same amount of gas he established the chemical equivalence of these substances.
The most familiar use of diamonds today is as gemstones used for adornment, a use which dates back into antiquity. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds. In the 20th century, experts in gemology have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds: these are carat, cut, color, and clarity. A large, flawless diamond is known as a paragon.
