Margarosanite and clinohedrite - Franklin, NJ
Margarosanite: fluorescent blue-white and pink, SW
Pectolite (?): fluorescent orange, SW
Willemite:  fluorescent green SW

Margarosanite {Pb(Ca,Mn)2Si3O9} is a rare and classic Franklin mineral that fluoresces blue-white (and sometimes pink) under shortwave UV. It was found, as far as I know, in only two locations: (1) the Parker / Palmer shafts of the Franklin mine in New Jersey, and (2) the Långban mine complex near Värmland, Sweden. Margarosanite is indeed rare, but its price has become quite high (especially for Franklin specimens).  This has made it difficult for the average collector to obtain, except in very small pieces like this one.  Quantitatively, margarosanite probably wasn't "that" rare at Franklin (I doubt it was as rare as cuspidine), but I think it's probably being selectively hoarded by collectors.  

This specimen is only about an inch-and-a-quarter across maximum dimension.  I've actually had it since my mom bought it for me as part of a set, which would have been around 1979.  The set contained a piece of hyalite opal from Spruce Pine.  At the time, I had a friend who had a rock and mineral set of his own (non-fluorescent), and I remember trading him a piece of that hyalite for one or two non-fluorescent rocks (ilmenite, I think, and stibnite).  At the time, I thought the margarosanite was cool, but that weird, glassy hyalite-- amorphous, but looking like a mass of branching, dendritic glass crystal-- was even cooler. 

Glad I didn't trade the margarosanite.

Anyway, it was part of a mini fluorescent collection being sold by the Franklin Mineral Museum.  I wish they still sold sets having rocks like these!    (Once you get under the 1 1/2 inch size range for fluorescent minerals, they become more affordable, by far.)


Another long-time collector has told me the orange-fluorescing material is pectolite.  I thought perhaps it could be wollastonite.   (Well, there's the possibility it's clinohedrite, but the assemblage and morphology are not familiar to me.)   I can tell you this much... whoever labeled it back in '79 at the museum had no idea, either, because the little piece of tape that used to be stuck to the rock said only "AXINITE,  WILLEMITE, MARGAROSANITE".  Maybe they ran out of room for the fourth mineral?  (This piece has axinite, but it's dim and there isn't much of it.)

Wollastonite has brief intense phosphorescence (BIP) or "flash".  I can't really tell if this piece "flashes" or not;  it seems to, ever so slightly.  However, it's not nearly as pronounced as you'd get with, say, calcite.

Well, I hope you liked this little story, and of course the margarosanite specimen.






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