Gahnite crystal in calcite

Gahnite: dark green (almost black) octahedral crystal
Calcite: white matrix, scraped away w/ screwdriver

Gahnite {ZnAl2O4} is a rare member of the spinel group. It's found in granular, massive, or sometimes crystalline form. Good crystals of any size are tough to find, the majority of them being misshapen or just plain broken. This specimen is the largest [intact] crystal of gahnite I've found at Sterling Hill. In order to expose it from the matrix, I scraped away the calcite with a small screwdriver-- a very tedious process that can take several evenings (at best).

I used an older Sony Mavica digital camera to take this picture. It's not that bad a picture, but I've considered re-photographing it with a newer setup.

Another view of the crystal

This crystal came from a recent (2000) field trip to the Passaic and Noble Pits at Sterling Hill. (Special thanks to the Sterling Hill Mining Museum and its owners for hosting the trip.) Crystals like this don't just fall into your bucket- you have to do some work for them. The point is, though, there's still great stuff being found-- another reason to get out there and do some field collecting!

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