Chalcedony is a mineral which consists of silicon dioxide. It is found in botryoidal, stalactite-like aggregates, in geodes, replacing fossils and other minerals. It is deposited from aqueous solutions at medium to low temperatures and is used as a decorative stone.
Amethyst is a variety of quartz that forms fine pyramidal crystals. Its name is of Greek origin. Its hardness is 7 and its specific gravity 2.65. It crystallizes in the orthorhombic crystallographic system and forms crystals in the shape of hexagonal prisms. It is an impressively beautiful material and meets all specifications to be used for crafting jewelry. However, its price is not very high because it is mined in large quantities. Ancient Greeks believed that amethyst could guard against drunkenness. In the Bible it is identified with the ninth tribe of Issachar and adorns the vestments of the high priest of the temple of Solomon.
Quartz is one of the most common minerals, making up almost 12% of the Earth’s crust It is also known as silicon dioxide and is encountered in sedimentary and volcanic rocks. When found at high temperature during the last phase of its precipitation, quartz crystallizes within only a few months. It is mined in Brazil, Japan, America and Switzerland.