A mineral’s luster is the overall appearance of its surface. It may have the sheen of polished metal, or of an unpolished metal that is pitted by weathering. It may have the sheen of glass, or look dull or earthy, etc. Luster should not be confused with color: A brass-yellow pyrite crystal has a metallic luster, but so does a shiny grey galena crystal . Quartz is said to have a glassy (or vitreous) luster, but its color may be purple, rose, yellow, or any of a wide range of hues. The different types of luster are:

Metallic, having the look of a polished metal, like the shiny side of aluminum foil; Submetallic, having the look of a metal that is dulled by weathering or corrosion, much like the non-shiny side of aluminum foil, and Non-metallic, not looking like a metal at all. Nonmetallic luster is divided into several sub-types:

Adamantine, having the hard, sparkly look of a diamond
Glassy/Vitreous, having the look of glass;
Resinous, having the look of amber – not quite glassy;
Pearly, having the iridescent look of mother-of-pearl (though usually just barely);
Greasy/Oily, having the look of an oil-coated substance;
Silky, having the look of silk, fine parallel fibers of mineral
Dull, having a plain looking surface that is not submetallic;
Earthy, having the look of soil or clay.

Certain minerals with a resinous or adamantine luster, such as sphalerite, can appear submetallic. Care needs to be taken in deciding which of these lusters a particular mineral has. Some minerals do not have an easily defined luster and are merely described as non-metallic.
Metallic Submetallic Nonmetallic