Willemite is most often found as compact, granular or massive aggregates. Well formed prismatic crystals are rare. Very rare idiomorphic crystals of willemite occur in Altenberg, Belgium. It may range in color from translucent to opaque and colorless to yellow-green, red, brown or black, with a resinous to vitreous luster.
While most willemite is not fluorescent, some varieties of flouresce with a bright green color when exposed to ultraviolet light. The very bright green fluorescence of some of the willemite from the Franklin and Sterling Hill mines makes specimens from those localities popular with fluorescent collectors. Some willemite is also known to be phosphorescent, that is, to continue to emit light after the ultraviolet source has been removed (glow in the dark). A variety which displays excellent fluorescent and phosphorescent properties occurs in Pinal County, AZ.
Rocks from Bob's Collection
Index of Specimen Images
Table of Contents