Post as a guest Name. Chatoyant minerals display luminous bands, which appear to move as the specimen is rotated. A submetallic lustre often occurs in near-opaque minerals with very high refractive indices,  such as sphalerite , cinnabar and cuprite. They are electronegative in character.
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Post as a guest Name. Email Required, but never shown. Featured on Meta. Custom Filters release announcement. Linked Related 2. Hot Network Questions. This ambiguity is further complicated by lustre's ability to vary widely within a particular mineral species.
The terms are frequently combined to describe intermediate types of lustre for example, a "vitreous greasy" lustre. Some minerals exhibit unusual optical phenomena, such as asterism the display of a star-shaped luminous area or chatoyancy the display of luminous bands, which appear to move as the specimen is rotated. A list of such phenomena is given below. Adamantine minerals possess a superlative lustre, which is most notably seen in diamond.
Minerals with a lesser but still relatively high degree of lustre are referred to as subadamantine , with some examples being garnet and corundum. Dull or earthy minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, approximating a Lambertian reflector. An example is kaolinite.
Greasy minerals resemble fat or grease. A greasy lustre often occurs in minerals containing a great abundance of microscopic inclusions, with examples including opal and cordierite , jadeite. Metallic or splendent minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface.
Examples include galena ,  pyrite  and magnetite. Pearly minerals consist of thin transparent co-planar sheets. Light reflecting from these layers give them a lustre reminiscent of pearls. 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 variety of gypsum. 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 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.
Waxy minerals have a lustre resembling wax. Examples include jade  and chalcedony. Asterism is the display of a star-shaped luminous area. It is seen in some sapphires and rubies , where it is caused by impurities of rutile. Aventurescence or aventurization is a reflectance effect like that of glitter. It arises from minute, preferentially oriented mineral platelets within the material.
These platelets are so numerous that they also influence the material's body colour. In aventurine quartz , chrome-bearing fuchsite makes for a green stone and various iron oxides make for a red stone. Chatoyant minerals display luminous bands, which appear to move as the specimen is rotated. Such minerals are composed of parallel fibers or contain fibrous voids or inclusions , which reflect light into a direction perpendicular to their orientation, thus forming narrow bands of light.
The most famous examples are tiger's eye and cymophane , but the effect may also occur in other minerals such as aquamarine , moonstone and tourmaline. Color change is most commonly found in alexandrite, a variety of chrysoberyl gemstones.