Willemite in Calcite

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Compared with most other world occurrences of Willemite where it forms as supergene secondary encrustations of crystals, the Willemite from Franklin Mining District is quite different, not only geologically, but crystallographically. Formed within a metamorphic environment, the Franklin Willemite is best known for its extremely vivid green fluorescence under short-wave UV light, but in natural light it is quite a dull-looking mineral. Forming a single, classic (for SterlingHill/Franklin), 1.5 cm long, stout prismatic crystal, grey-brown in colour partially embedded in cleaved white Calcite, this presents a really excellent individual Willemite crystal. Miniature in size, this specimen makes a fine smaller display piece, especially with how the Willemite crystal is exposed, perched upon the Calcite. There are certainly not many perfect individual Willemite crystals like this, even within specialist Franklin collections. We have not checked this one out for fluorescence but would expect the Calcite to be vivid orange under SW UV light, but whether the Willemite fluoresces is unknown. Ex David Hardman Collection.