Franklinite: opaque, black, submetallic octahedral crystal
Calcite: whitish matrix

Franklinite is an oxide of zinc, manganese, and iron. A member of the spinel group, its crystals are usually octahedral... when it's not in massive or granular form, which is what I usually find on collecting trips.
This nice specimen is the result of countless attempts to recover an intact crystal from a franklinite - calcite - willemite boulder that sits on the Mine Run Dump at Sterling Hill. Most of the other ones broke during the careful "extraction" process, which includes at some point hammering and chiseling on the boulder to loosen chunks of matrix rock. Quality of specimens seems to be directly proportional to the time spent on that boulder and inversely proportional to the number of pieces knocked loose with any one hammer swing...
If you are going to collect franklinite crystals and don't plan to spend insane amounts of money at mineral shows, I suggest getting into micromounting... the best, sharpest crystals to be found nowadays are less than 1.5 millimeters across. The one pictured above is a whopping 5 millimeters in largest dimension : )

By the way, don't form your opinion of my photography skills from these old digital pictures. I may re-photograph with better cameras / lighting, if time permits (and I can still find that specimen).

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