The chemical composition of garnet is A3B2[SiO4]3, where A is Ca, Fe, Mg, and Mn, and B represents Al and Cr. Garnet is a collective term for the garnet family of minerals. Its colour varies from blood red, dark red, reddish brown, brownish yellow, yellowish green, and bright green to black. It has a vitreous lustre, whereas the fracture lustre is greasy. The specific gravity is 3.1–4.3, the Mohs hardness is 6.5–7.5, and it is a typical high-temperature and metamorphic mineral. It is a common gemstone mineral ore. The main gem varieties include pyrope, rhodolite, grossular, almandite, spessartine and andradite. Pyrope and rhodolite have bright red colours, and in Chinese, they are called ‘dark purple teeth’. Garnets have a wide natural distribution and are used mainly as gems or for grinding.