Lustre is the way light interacts with the surface of a crystal, rock, or mineral and generally implies radiance, gloss, or brilliance.Dull (or earthy) minerals exhibit little to no lustre, due to rough or powdery surface. An example is
Metallic (or splendent) minerals have the lustre of polished metal, and will work as a reflective surface. Examples include galena, pyrite and magnetite.
Pearly minerals consist of thin transparent sheets. Light reflecting from these layers give them a lustre reminiscent of pearls with examples including muscovite and stilbite.
Resinous minerals have the appearance of resin, chewing gum or (smooth-surfaced) plastic. A principal example is amber, which is a form of fossilized resin.
Silky minerals have a parallel arrangement of extremely fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos, ulexite and the satin spar Selenite. A fibrous lustre is similar, but has a coarser texture.
Submetallic minerals have similar lustre to metal, but are duller and less reflective. A submetallic lustre often occurs in near-opaque minerals with very high refractive indices, such as sphalerite, cinnabar, anthracite, and cuprite.
Vitreous minerals have the lustre of glass. (The term is derived from the Latin for glass, vitrum.) This type of lustre is one of the most commonly seen and occurs in transparent or translucent minerals with relatively low refractive indices. Common examples include calcite, quartz, topaz, beryl, tourmaline and fluorite, among others.
Waxy minerals have a lustre resembling wax. Examples include jade and chalcedony.
The amount of light able to be passed through a mineral determines its transparency. Light is able to pass through transparent minerals; translucent minerals partially let light pass through; and opaque minerals do not let any light through.