Fluorescent Mineral Database

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The exsolution game... Willemite, calcite and tephroite.

Contributed by: Axel Emmermann
minID:
Date: Jan 23rd, 2025
Locality: Franklin Mine, Franklin, Sussex County, New Jersey, USA (See on Mindat)

Description:
The labels of specimens like this nearly always read \"Calcite & willemite\". They never mention the non-fluorescent massive brown stuff, the tephroite. Exsolution of willemite from zincian tephroite happens during cooling. The expelled willemite is deposited in cracks that form in the shrinking mass, following the surface of the tephroite crystallographic planes. Hence the neatly ordered fine lines. (Thanks to Earl Verbeek for the explanation.) The calcite just adds to the fun...

Fluorescence under shortwave UV light.
Fluorescence under shortwave UV light.

Summary of luminescence responses:

Willemite

  • Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green
Calcite
  • Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Red

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