Gemstones are minerals that have a beautiful appearance (usually only after polishing or cutting) and at the same time are quite rare and, as a result, expensive. They are widely used for the manufacture of jewelry, assembled in collections, and used as banking assets. Imperceptible-looking imitations of most gemstones are made artificially, imitations or fakes of many gemstones were made even in the times of Ancient Rome (today such synthetic stones and imitations of gems are very popular, since they cost much less). In 1902, the French chemist M. A. Verneil first received and began to supply synthetic rubies to the world market, and a little later, synthetic sapphires and synthetic spinel. The appearance of a large number of synthetic stones did not reduce, but, on the contrary, increased the value and cost of natural, natural gems. Less rare minerals are often called semiprecious.