Willemite Var. Troostite – Sterling Mine, Franklin, New Jersey, USA

A manganese-rich variety of willemite from the zinc mines of the Franklin District of New Jersey.
Sharp and geometric crystals of willemite, as seen here, are rarer than the typical grains seen in specimens from Franklin, New Jersey, embedded in calcite, franklinite and zincite. The largest crystal on this piece is a remarkable 3 cm in size. As is to be expected from Franklin minerals, the troostite crystals fluoresce light green under short-wave UV light and form a beautiful contrast to the calcite in which they are embedded.
The possibility of finding them has been extinct since the 1970s!