Mineral lustre is the capacity of a mineral surface to reflect visible light. The intensity of the mineral lustre depends on the refractive index, absorption coefficient and reflectivity of the mineral. In mineralogy, there are four levels of lustre from strong to weak: (1) metallic lustre, (2) submetallic lustre, (3) adamantine lustre, and (4) vitreous lustre. The adamantine and vitreous lustres are collectively known as nonmetallic lustre. Nonmetallic minerals are generally characterized by nonmetallic lustres, whereas metallic minerals are metallic or submetallic. The intensity of the mineral lustre is based on the reflection of the crystal surface and the cleavage surface. Several other reflective surfaces and aggregate forms can create unique lustres, such as pearly lustre, greasy lustre, resinous lustre, silky lustre, waxy lustre and dull lustre.