The Franklin Mine in Franklin, New Jersey, and the Sterling Hill Mine in Ogdensburg, New Jersey, are the most important localities for this otherwise uncommon mineral. These two mines in the same zinc ore body have produced interesting specimens of Willemite of all shapes, habits, and colors in abundance. The only other U.S. locality of importance is the Mammoth-St. Anthony Mine, Tiger, Pinal Co., Arizona, which has produced small crystals of Willemite together with Wulfenite. Botryoidal
Willemite groups are found in the Potosí Mine, Santa Eulalia District, Chihuahua, Mexico. Brown, drusy
crystals were found in the type locality
at Kelmis, Moresnet, Belgium. In Namibia, Berg Aukas, in the Grootfontein District, produces acicular
Willemite crystals. The most significant locality after the Franklin District is Tsumeb, Namibia, which has produced beautifully colored botryoidal
and ball shaped aggregates of white, green, yellow, and blue Willemite. The most prized Tsumeb colors are the deep blue and cadmium-rich deep yellow.