willemite

{{Infobox mineral | name = Willemite | category = Silicate mineral | boxwidth = | boxbgcolor = | image = File:Willemite-168225.jpg | imagesize = | caption = Willemite from Namibia | formula = | IMAsymbol = Wlm | molweight = | strunz = 9.AA.05 (10 ed) 8/A.01-20 (8 ed) | dana = 51.1.1.2 | system = Trigonal | class = Rhombohedral () (same H-M symbol) | symmetry = R | color = Colorless to white, gray, black, flesh-red, burgundy-red, pink, brown, dark brown, mahogany-brown, honey-yellow, yellow, apple-green, blue, pastel green, light blue, azure-blue | habit = Fibrous, botryoidal to massive | twinning = | cleavage = {0001}, {110} – imperfect | fracture = Irregular to conchoidal | mohs = 5.5 | luster = Vitreous to resinous | refractive = nω = 1.6911.694 nε = 1.7191.725 | opticalprop = Uniaxial (+) | birefringence = δ = 0.028 | pleochroism = | streak = | gravity = 3.94.2 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to opaque | other = Strongly fluorescent; may be phosphorescent | var1 = troostite | var1text = zinc is partly replaced by manganese | references = }}

Willemite is a zinc silicate mineral () and a minor ore of zinc. It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in a variety of colors in daylight, in fibrous masses and apple-green gemmy masses. Troostite is a variant in which part of the zinc is partly replaced by manganese, it occurs in solid brown masses.