Championjewelery.us

Minerals reflect light to a very varying degree. The lustre of a mineral depends partly on its ability to reflect light and partly on the degree of its transparency, its refractive index and the nature of its surface. Lustre is described by terms which compare the mineral’s surface to that of well-known objects. It may thus be metallic, adamantine (i. e. like diamond used for diamond rings), vitreous, waxy, pearly, porcellanous, resinous or silky, to mention just a few common examples. Minerals with metallic lustre are usually opaque and often have a mirror-like surface. The degree of intensity of the lustre is thus also recorded, and we talk of a mineral being shining, glistening, glimmering or dull. The degree of lustre of a mineral is greatly reduced if its surface is covered with a thin film or incrustation of another mineral, or if there are signs of weathering. Earthy mineral aggregates always have a dull lustre.