有关珍珠的论文文献

A pearl is a hard, roundish object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of mollusks, a pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of pearls (baroque pearls) finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries, and because of this, the word pearl became a metaphor for something very rare, very fine, very admirable and very any shelled mollusk can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within the mollusk's mantle folds, but virtually none of these "pearls" are valued as gemstones. Although malacologists may refer to these objects as "pearls", gemologists classify them merely as calcareous black pearl and a shell of the black-lipped pearl oyster Saltwater pearl oyster farm, Seram, IndonesiaNacreous pearls, the most desirable pearls, are produced by two groups of molluscan bivalves or clams. One family lives in the sea: the pearl oysters. The other, very different group of bivalves live in freshwater, and these are the river mussels; for example, see the freshwater pearl 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. These various species of bivalves are able to make nacreous pearls because they have a thick iridescent inner shell layer called "mother of pearl", which is composed of nacre. The mantle tissue of a living bivalve can create a pearl in the same manner that it creates the pearly inner layer of the gem-quality saltwater and freshwater pearls can and do sometimes occur completely naturally in the wild state, but this is 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. In modern times however, almost all the pearls for sale were formed with a good deal of expert intervention from human pearl pearl being extracted from an akoya pearl oysterA nacreous pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell. A "natural pearl" is one that formed without any human intervention at all, in the wild, and is very rare. A "cultured pearl", on the other hand, is one that has been formed on a pearl farm. The great majority of pearls on the market are cultured or fake pearls are also widely sold in inexpensive jewelry, but the quality of the iridescence is usually very poor, and generally speaking, fake pearls are usually quite easy to distinguish from the real have been harvested, or more recently cultivated, primarily for use in jewelry, but in the past they were also stitched onto lavish clothing, as worn, for example, by royalty. Pearls have also been crushed and used in cosmetics, medicines, or in paint is considered to be the birthstone for the month of June.

毫无疑问,珍珠是非常昂贵的,它之所以昂贵,完全是体现于它自身历经的磨难和自身的价值.珍珠是十分漂亮的,而这漂亮的外表背后,却有着一个感人的故事.其实,珍珠形成的过程是非常痛苦的.在茫茫的大海底下,生活着蚌,而每个蚌的体内都会都会进入一粒沙子,蚌要忍痛的每天对沙子磨啊磨,磨啊磨,最后就会把沙子磨成一颗璀璨的珍珠.所以现在我们眼中那一颗颗动人的珍珠,其实就是由一粒粒普通的沙子变成的.还有一个恰恰相反的例子.有一粒沙,见到周围的伙伴钻进蚌的体内后,都变成了珍珠,羡慕不已,于是下决心向他们学习,以证明自己的价值.它请求一只蚌让自己钻进它的贝壳里,梦想着变成一粒美丽的珍珠.没过多久,砂的周身被蚌分泌出的白色粘液包裹起来,越裹越紧,让它透不过气来.砂想,原来变成珍珠的过程这么痛苦,我再也不要做什么珍珠了.砂终于禁不起痛苦的磨炼,被蚌吐回了海底,而它的伙伴们都变成了珍珠.珍珠与砂的价值天壤之别,可细想想,它们之间相差的又只是短短的那么一段过程和经历.人又何尝不是如此呢?我们每个人原本都能成为一粒美丽的珍珠,却往往因为种种个性上的弱点和行为上的偏差,失去了原有的光泽和慧质,而仅仅是一粒沙.为什么不现在就除去人性中的弱点,使自己更加完美呢?你也是一颗珍珠,应该照亮自己的人生.在人生的漫漫路途中,我们应该能经受得起命运给予我们的每一次磨难,使自己在种种磨难中逐渐成长,逐渐坚强,使自己从一粒普通的沙子变成一颗璀璨的珍珠,我们要在人群中出类拔萃,要成为人群中的闪光点.清晨,面对镜子中的自己,我们应该微笑的面对,不要苦恼,不要忧愁,要记住,你也是一颗珍珠.

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