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Natural pearls are formed when an foreign object becomes trapped in the shell of an oyster or pearl and the animal surrounds the object with several mineral layers in order to protect its soft tissue. Most pearls sold today are farmed pearls, created by intentionally inserting small mother-of-pearl beads in the oyster's shell. The resulting pearls are harvested up to two years later. Pearls come in a range of pastel colors from cream to blue to pink, and irregularly shaped pearls are often called "baroque" pearls. Mabe pearls are hemispherical cultured pearls grown against the inside shell of an oyster rather than in the mollusk's body. Mabe pearls are typically used in settings such as that conceal their flat backs. The relatively abundant mineral smoky quartz ranges in color from almost black to nearly colorless. Gem quality specimens are mined from the Swiss Alps and from Pike's Peak in Colorado. Dark smoky quartz is sometimes heat-treated to give it a lighter color which appears more brilliant when cut. Opaque and royal blue with white veins, sodalite is found all over the world, sometimes in huge deposits. Often mistaken for lapis lazuli because of its color, sodalite has been used for decorative purposes since Egyptian times. Today, in addition to its decorative uses, a sodalite solution is used in some commercial swimming pool test kits. Beautiful turquoise is a phosphate mineral popular all over the world. Mined since 5000 BC, it is one of the first gemstones known to be used by humans. Color variation from sky-blue to medium green is affected by differing amounts of copper and iron, more copper giving the stone a bluer color and more iron a greener one. Beautiful light blue turquoise is mined in Northern Iran and other varieties occur in Mexico, the United States and elsewhere.
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