Tumbled stones of Aquamarine quality. B from Brazil, cut in India.

Gemstones are rare rocks, which are usually processed and incorporated into jewelry and decorative objects. Gemstones have the following characteristics: Beauty. This includes visual aspects such as color, gloss, fire, transparency and lighting effects. Sustainability. This involves looking at hardness, fragility, splitting and chemical resistance. Rarity. This looks at how often a product occurs in nature. Gemstones can be cut into many different shapes. The basic distinction is made between cabochon, where the gemstone is cut into a convex shape, and faceted, where the surface of the gemstone is cut into different facets. When grinding, various properties of the stone are considered, including the color, color distribution, inclusions, special light effects, dispersion and fracture and wear surfaces. They are processed into necklaces, earrings, bracelets and many other jewelry, but the gemstones are also used in industry for processing. Well-known gemstones include diamond, ruby, emerald, sapphire, aquamarine, topaz, tourmaline, amethyst, citrine, carnelian, opal, onyx, turquoise, lapis lazuli and garnet. In the 18th and early 19th centuries it was fashionable to make jewelry containing someone's name or initials. When choosing the gemstones, they were guided by the first letter of the name of the gemstone, and thus the gemstone alphabet was created. Similar achrostic jewelry was also made during the nineteenth century in which sentiments were expressed in gemstones. The best known is the English 'regard' ring, an engagement ring in which the word 'regard' was formed by the gemstones ruby, emerald, garnet, amethyst, diamond.