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贝壳里的珍珠是怎么来的
更新时间: 2021-01-25 06:11:15  

1、当蚌的贝壳张开时,外界的泥沙,寄生虫等异物偶尔掉进去。

2、外套膜受到刺激,它就会分泌出珍珠质。

3、把掉进去的异物裹住,逐渐形成珍珠囊。

4、这样,经过很长一段时间,就会变成晶莹圆润,细腻光滑的珍珠。

5、珍珠的成分是碳酸钙。

关键词: 贝壳 珍珠 怎么

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