Metallic minerals are used for the extraction of metals, and they mainly include non-ferrous metal, ferrous metal, precious metal and rare metal minerals. Metallic minerals generally have metallic properties, such as a metallic or submetallic lustre, high opacity, good conductance and good thermal conductivity. Most are sulphides, some are oxides, and some are elemental metals. There are exceptions, such as sphalerite, cinnabar and cassiterite, which do not have typical metallic properties. Graphite has obvious metallic properties but is not a metallic mineral. With appropriate treatment, crystals or mineral aggregates can have high ornamental value.