Ca₃PbZn₄(SiO₄)₄

Description

Esperite is a rare mineral, but was found locally in the north end of the Franklin mine in masses of at least many kilograms weight. It is known only from Franklin and in minute amounts from a mine in Bolivia.

Esperite and willemite. Fluorescing yellow and green, respectively, under short-wave UV. Franklin, NJ. Width 16 cm.

Esperite is brilliantly fluorescent yellow under short-wave ultraviolet light, in some cases it is even more brilliant than the often associated willemite.

Much esperite appears to have replaced other primary minerals, such as hardystonite, and these specimens often provide complex textures of several fluorescent minerals, making some of the most striking fluorescent specimens known. Good specimens are prized.

Daylight view

Esperite, willemite, calcite. Fluorescing yellow, green, and red, respectively, with under short-wave UV. Franklin, NJ. Width 4 cm.

Daylight view

Esperite and willemite. Fluorescing yellow and green, respectively, under short-wave UV. Sawn surface. Franklin, NJ. Width 10 cm.

Daylight view

Esperite and willemite. Fluorescing yellow and green, respectively, under short-wave UV. Esperite here occupies fractures in a mixture of franklinite/garnet. Franklin, NJ. Width 4 cm.

Be sure to visit the photo page taken under shortwave ultraviolet light.

For more information on esperite, see Dunn (1995).