{"id":6765,"date":"2012-07-12T00:00:00","date_gmt":"2012-07-11T22:00:00","guid":{"rendered":"https:\/\/www.genisi.com\/do-you-know-the-south-sea-pearls\/"},"modified":"2012-07-12T00:00:00","modified_gmt":"2012-07-11T22:00:00","slug":"do-you-know-the-south-sea-pearls","status":"publish","type":"post","link":"https:\/\/www.genisi.com\/en\/do-you-know-the-south-sea-pearls\/","title":{"rendered":"Do you know the South Sea pearls ?"},"content":{"rendered":"

The expression “South Sea pearl” is a commercial term used by pearl farmers and dealers. This name, so evocative of tropical seas, refers to the large pearls produced by two species<\/strong> of pearl oyster<\/strong>,\u00a0or pteridean<\/strong>, of considerable size, which live in these\u00a0warm seas. The white-lip pearl oyster, Pinctada\u00a0maxima<\/strong>, includes two varieties, the gold-lip<\/strong>, which\u00a0gives golden coloured pearls, and the silver-lip\u00a0<\/strong>which gives white pearls. The black Pinctada margaritifera<\/strong>, whose deep-sided shell
\nmeasures about 25 cm, produces the black pearl<\/strong>.<\/p>\n

\"\"
A large black produced by a Pinctada Margaritifera<\/figcaption><\/figure>\n

Exceptionally large baroque pearl harvested from pinctada maxima<\/p>\n

To succeed in growing cultured pearls<\/strong>, man harnesses the cellular activity of three aquatic bivalve\u00a0molluscs.\u00a0First a spherical nucleus has to be carved from\u00a0the thick layer of mother-of-pearl in the shell of a freshwater mussel, a unionid<\/strong>. In these shells the calcium\u00a0carbonate is crystallized as aragonite. The mother-\u00a0of-pearl, secreted by the mantle, is composed of\u00a0thousands of parallel layers of tabular crystals<\/strong>. Each\u00a0layer of aragonite lies on a thin organic film. The\u00a0grafter cuts out a piece of tissue from the mantle of a\u00a0marine pearl oyster, places it over the nucleus, and\u00a0inserts this ensemble, or graft, into the genital gland\u00a0of another pearl oyster of the same species. The\u00a0grafted oyster is put back into the sea for several\u00a0more years, and slowly the cells of the graft cover\u00a0the nucleus with a layer of mother-of-pearl, or\u00a0nacre. ln the cultured pearl, this forms layers of aragonite alternating with leaflets of an organic matrix.
\nHowever, instead of being arranged flat as in the\u00a0oyster shell, the layers are positioned concentrically\u00a0around the nucleus.
\nThe cultured pearl is thus composed entirely of\u00a0nacre<\/strong>, that of the nucleus being freshwater in origin,\u00a0while the outer part, marine<\/strong>. Grafters have tried to\u00a0replace the nacre from Unios by nuclei of marine\u00a0mother-of-pearl, reconstituted nacre, and even\u00a0marble, but without satisfactory results. At present\u00a0all cultured pearl nuclei come from the shells of the\u00a0freshwater Mississippi mussel<\/strong>, or << pig toe >>, which\u00a0is threatened by over-exploitation. To succeed in pro-\u00a0ducing a cultured pearl, two pearl oysters, a donor\u00a0and a recipient, are needed. To preserve the species, therefore, pearl oyster breeding should be
\ndevelopped further.\u00a0In natural or fine pearls, the nucleus is provided\u00a0by a parasitic intruder, which the oyster isolates first in
\na sac formed by the mantle, and then in a pearly\u00a0envelope. Natural pearls<\/strong> thus rarely have solid nuclei.
\nIn the past, the craze for natural pearls led to the\u00a0exploitation of millions of oysters. This practice eventually brought about the destruction of most of the natural pearl oyster beds. Natural pearls can still be found in some freshwater pearl mussels. However, these are\u00a0worth much less. The only natural thing about the\u00a0imitation pearl, beautiful though it may be, is the coat
\nof iridescent guanine, obtained from fish scales, with\u00a0which it is varnished.
\nCultured South Sea pearls<\/strong> are of remarkable\u00a0size. The considerable space inside the larger pearl\u00a0oysters allows implantation of large nuclei. Moreover the pearl nacre is laid down faster than in the\u00a0smaller species, giving a thicker final coating around\u00a0the nucleus. The diameter of these pearls ranges\u00a0from 9 to 20 mm<\/strong>, while baroque pearls can reach\u00a0a length of AO mm. The pearl nacre can vary in\u00a0thickness from 2 to o mm, and it is the quality of the\u00a0nacre which can give a pearl an exceptional orient\u00a0and lustre. Pearls from small cold-water pearl oysters, by comparison, rarely succeed in coating the\u00a0nucleus with more than O2 to 0.6 mm.<\/p>\n","protected":false},"excerpt":{"rendered":"

The expression “South Sea pearl” is a commercial term used by pearl farmers and dealers. This name, so evocative of tropical seas, refers to the large pearls produced by two species of pearl oyster,\u00a0or pteridean, of considerable size, which live in these\u00a0warm seas. The white-lip pearl oyster, Pinctada\u00a0maxima, includes two varieties, the gold-lip, which\u00a0gives golden […]<\/p>\n","protected":false},"author":1,"featured_media":4308,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[743],"tags":[744],"class_list":["post-6765","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-rare-pearls","tag-south-sea-pearls"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/posts\/6765","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/comments?post=6765"}],"version-history":[{"count":0,"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/posts\/6765\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/media\/4308"}],"wp:attachment":[{"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/media?parent=6765"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/categories?post=6765"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.genisi.com\/en\/wp-json\/wp\/v2\/tags?post=6765"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}