国产av不卡一区二区_欧美xxxx做受欧美_成年人看的毛片_亚洲第一天堂在线观看_亚洲午夜精品久久久中文影院av_8x8ⅹ国产精品一区二区二区_久久精品国产sm调教网站演员_亚洲av综合色区无码一二三区_成人免费激情视频_国产九九九视频

珍珠歷來受到人們的喜愛和贊賞，名貴的珍珠可以與最尊貴的寶石相提并論。光是漢語中和珍珠有關的詞匯就有很多，比如“珠圓玉潤”，“玉貌珠顏”，“珠光寶氣”等等等等。天然珍珠的產量是十分稀少的，因此人們開創了養殖珍珠的方法。下面這篇短文將為您介紹珍珠是如何養殖的。

About 4,000 years ago the Chinese discovered pearls inoysters. The inside of an oyster's shell is covered with a smooth shiny coating called mother-of-pearl. When anirritant, such as a grain of sand, gets caught inside the oyster's shell it secretes layers of mother-of-pearl to protect its body by coating the irritant. The coated grain of sand becomes a pearl.

Man can force the oyster to produce a pearl by inserting an irritant into the shell. It takes the oyster two to three years to produce a good size pearl. Cultured pearls are usually not perfect, but the Japanese have discovered that if you surgically insert an irritant directly into the body of the oyster this will produce a perfect pearl.

Historically, pearl divers dove up to 80 feet with equipment no more sophisticated than nose clips. The divers could stay under water for about a minute and they scooped up the shells with their hands and put them in tubs that would float to the surface. The largest pearl ever found is reported to be four inches around and two inches long.

oysters: 牡蠣

irritant: 刺激物

（英語點津 Annabel 編輯）