instruction: Based on the given text, List some aspects of the pearl.
context: 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 fossil conulariids. 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 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 of 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.
response: 1.	Pearl is a sparkling and hard object which is produced inside mollusk shell or other shells.
  2.	Just like the shells pearls are also composed of calcium carbonate.
  3.	The Ideal pearl is perfectly round and smooth, but it can come in different shapes like baroque pearls.
  4.	The best quality natural pearls are valued as gemstones.
  5.	Since pearls are fine, rare and valuable it has become a metaphor.