Sphalerite from Ogdensburg

Sphalerite: FL tangerine to pinkish-orange
Franklinite: non-fluorescent regions

Sphalerite {ZnS} is mainly zinc sulfide but contains varying amounts of iron and often traces of cadmium and manganese as well. The best grades of fluorescent sphalerite contain very little or no iron. Locally, the term "cleiophane" describes the nearly iron-free sphalerite, especially the variety that fluoresces blue in long-wave and sometimes short-wave UV.

This specimen was from the collection of a miner who had worked for years at Sterling Hill. In normal light the sphalerite is a sparkly, translucent silver to golden color- readily distinguishable from most other minerals of the locality.

Transparent to translucent sphalerite has so much "sparkle" because it has an exceptionally high index of refraction. Its R.I. is close to that of diamond, but sphalerite has more "fire" or dispersion than diamond.  Its luster is called "adamantine", which means "diamond-like", because sphalerite crystals are so reflective.

The specimen shown above is about 3 inches across, if I remember correctly.


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