Specimen measures about 4 inches long. I found this on the Buckwheat Dump at Franklin, New Jersey back in the 1980's.
I know this is not a great photograph. Someday perhaps there will be a better one here, if I get the chance.
It was 1985, if I remember correctly. My mom took me to the Buckwheat Dump. I had the smallest Estwing rock pick and not much else. I was going around the dump here and there, collecting specimens, when I happened upon a fairly large ore rock. I knew ore rocks were good, because that's where the willemite usually was. (When I say "ore" I mean there's a lot of franklinite). So I spalled off a piece of this rock with my little Estwing, and right about then my mom said something like "Come on, let's go. Haven't you had enough of these rocks?".
So we left, and I took that little piece home with me. I left the remainder of that rock on the dump. I'd say the original rock was the size of a canteloupe. What are the odds that, on the whole rock, I'd have spalled off just the section that was cuspidine? I say the rock had to be solid cuspidine. Maybe you, the reader, found the rest of this rock and have it stashed in the basement now.
Anyway, when I saw the fluorescent color I couldn't believe it. Why, why, why did I not take the whole rock?! It's like a hazy dream, where there's this only this one part that I vividly remember: spalling off that specimen, being told we had to go now... but I don't remember why I didn't just take the whole rock. Not that I knew at the time what it was, because I didn't. I just knew when I lamped it (later) that it was like no other rock I'd ever found.
Some background on the I.D. of this specimen:
For at least ten or twelve years I hadn't the remotest idea of what it was. This was very puzzling. It wasn't in any of the books I could find on Franklin. The best color reference I had at the time was Nature's Hidden Rainbows, and it wasn't in there.
The first time I showed this rock to John Cianciulli, he said it was johnbaumite. That was around 1998. Then, later, he said it was cuspidine. That was right after Dru W. found some small cuspidine specimens, which resembled mine very closely. In fact, to look at them you'd think they were broken off the same rock, although his finds came from a chunk that was stuck in concrete. I think that was in 2000 but can't remember exactly.
I've seen a couple of other Franklin cuspidines - not the assemblage with nasonite mentioned in Dunn (1995), but the massive, fluorescent material that has been recovered a couple times from the dumps. Kurt H. and Fred L. have also found a few specimens on the Buckwheat after many months of searching.
I found another specimen on the Buckwheat (Nov. 1, 2005) consisting of spots of this mineral in calcite with hardystonite, franklinite, and another non-fluorescent mineral that's pinkish-purple in daylight. There is now another section for this specimen, with its own photo.
There should be a relatively straightforward chemical method to distinguish between cuspidine and johnbaumite. The latter mineral contains an arsenate group, while the former does not. The good old ammonium molybdate test should distinguish between them-- something I'll do when I get the time. It is fairly sensitive, so the amount of sample sacrificed will be minimal. Ammonium molybdate will react with either arsenates or phosphates to produce a yellow coloration; it's more sensitive to phosphate than arsenate if I remember correctly, but it should still serve.
Anyway, I still think about the chunk of cuspidine that I left there as a kid, years ago.
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