<P> A pearl is a hard glistening object produced within the soft tissue ( specifically the mantle ) of a living shelled mollusk or another animal , such as a conulariid . Just like the shell of a mollusk , a pearl is composed of calcium carbonate ( mainly aragonite or a mixture of aragonite and calcite ) in minute crystalline form , which has been deposited in concentric layers . The ideal pearl is perfectly round and smooth , but many other shapes , known as baroque pearls , can occur . The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries . Because of this , pearl has become a metaphor for something rare , fine , admirable and valuable . </P>
<P> A pearl is a hard glistening object produced within the soft tissue ( specifically the mantle ) of a living shelled mollusk or another animal , such as a conulariid . Just like the shell of a mollusk , a pearl is composed of calcium carbonate ( mainly aragonite or a mixture of aragonite and calcite ) in minute crystalline form , which has been deposited in concentric layers . The ideal pearl is perfectly round and smooth , but many other shapes , known as baroque pearls , can occur . The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries . Because of this , pearl has become a metaphor for something rare , fine , admirable and valuable . </P>
which gem stone is produced by the secretion of some sea creatures
which gem stone is produced by the secretion of some sea creatures
pearl
pearl