free download PNG images :Pearls

Pearls are hard objects produced in the soft tissues (especially mantle) of living mollusks with shells or other animals (such as ovals). Like the shells of mollusks, pearls are made up of microcrystalline calcium carbonate (mainly aragonite or a mixture of aragonite and calcite) and have been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but there are many other shapes that can appear, called baroque pearls. For hundreds of years, the best natural pearls have been regarded as gemstones and beautiful objects. Therefore, pearl has become a metaphor of rare, exquisite, admirable and valuable things.

The most valuable pearl occurs naturally in the natural environment, but it is extremely rare. These wild pearls are called natural pearls. Cultured or cultured pearls from pearl oysters and freshwater mussels account for the majority of current sales. Artificial pearls are also widely sold in the form of cheap jewelry, but their iridescent quality is usually poor and can be easily distinguished from real pearls. Pearls are mainly harvested and planted for jewelry, but they have also been used for decorative clothing in the past. They have also been crushed and used in cosmetics, pharmaceuticals and paint formulations.

Whether wild or cultured, pearls of pearl quality are almost always pearly and iridescent, just like the inner shell that produces them. However, almost all mollusc species with shells can produce pearls with smaller luster or spherical shape (technically known as "calcareous stones"). Although these gemstones may also be legitimately called "pearls" under the regulations of gemmology laboratory and the Federal Trade Commission of the United States, and they are formed in the same way, most of them have no value except curiosity.