Nasonite, Prehnite, Margarosanite, et al. from the Franklin Mine, NJ

Contributed by: Simone Conti
minID: TNK-70U
Date: Sep 18th, 2026
Locality: Franklin Mine, Franklin, Sussex County, New Jersey, USA (See on Mindat)
Size: 5 x 3 x 5 cm
Weight: 64.1 g

Description:
A nice example of “Parker Shaft Soup” mix of minerals. The two most obvious minerals are margarosonite, fluorescent bright light blue under shortwave UV light, and axinite-Mn, fluorescent red under any wavelength, brightest under longwave. But there is obviously more than just those two minerals. On the first side alone we can see the bright blue/white fluorescence of margarosanite, red of axinite, a darker red (still axinite?), a dark blue from xonotlite, violet/lilac from prehnite, grey from nasonite, orange from clinohedrite with orange afterglow, and the green of willemite. On side 2 we have a lot of margarosonite and axinite, plus a bit of grey/brown from nasonite. On side 3 we have a lot of the same colors again, with an extra pink from prehnite, and again some of the grey/brown (which now fluoresces brown/yellow longwave). There is not much of the typical red afterglow/BIP of calcite, so I exclude it from the mineral list. Now, some of these identifications are a little bit speculative, and I don’t have confirmatory analyses. Particularly the nasonite/prehnite: these are hard to ID, and there are not too many photos availabile (or accessible samples!) to compare to. Take it with a grain of salt. Photos are for all four sides, under normal light, shortwave, midwave, and longwave UV light. The midwave response is about 5 times weaker (5 times longer exposure), while shortwave and longwave are similar exposures.