Franklinite

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The Franklin Mining District in Sussex County, New Jersey, USA, is one of those very few places on the Earth where nature has concentrated an astonishing variety of mineral species, in the case of Franklin, some 255, of which it is type locality to a staggering 49. The ore body follows an anticline with the Franklin mines developed at one end where it crops out, the equally famous Sterling Hill mines developed at the opposite outcrop close to Ogdensberg. where the species count climbs to 269 with 25 type localities. This splendid cabinet specimen contains several Franklinite crystals, a zinc-iron oxide belonging to the Spinel Group, set in a matrix of white Calcite with more minor pink-brown Willemite. The Franklinite forms black octohedral crystals, with one exceeding 2 cm on edge (2.3 x 2. cm), this being the centre of focus on the specimen. Under SWUV the Franklinite remains black as it is non-fluorescent, whereas the Calcite glows hot-coal scarlet and in the lower half of the matrix, the Willemite fluoresces smack-you-in-the-chops intense lime green. A Franklin classic!