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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.
The most valuable pearls occur spontaneously in the wild, but are extremely rare. These wild pearls are referred to as natural pearls. Cultured or farmed pearls from pearl oysters and freshwater mussels make up the majority of those currently sold.
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Porto Velho (Portuguese pronunciation: [ˈpoʁtu ˈvɛʎu], Old Port) is the capital of the Brazilian state of Rondônia, in the upper Amazon River basin, and a Catholic Metropolitan Archbishopric. The population is 519,531 people (as of the IBGE 2018 estimation). Located on the border of Rondônia and the state of Amazonas, the town is an important trading center for cassiterite, the mining of which represents the most important economic activity in the region, as well as a transportation and communication center.
Nuuk (Greenlandic pronunciation: [nuːk], Danish: [ˈnu(ː)k]; Danish: Godthåb [ˈkʌtˌhɔˀp]) is the...
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Aarau (German: [ˈaːraʊ], Swiss German: [ˈɑːræu̯]) is a town, a municipality, and the capital of...