Sphalerite, Willemite, and Franklinite - Sterling Hill Mine, New Jersey

Contributed by: FMS Admin
Date: May 8th, 2026
Locality: Sterling Mine, Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA (See on Mindat)
Weight: 6 lb

Description:
Sphalerite is a stunning material, and apparently quite varied in its manifestations. This Sterling Hill Mine specimen is a rather large piece, over six pounds, and is quite beautiful in its patterns. Apparently, the sphalerite is both blue and orange, though it appears to be more pink in spots. More on that below. In this case, the willemite is of the troosite variety, and a brick red color.

From Earl Verbeek, Franklin Mineral Museum via Facebook: "At least two different activators. The orange emission is due to manganese. The blue emission has been ascribed to silver, but I don't know of any proof of that. A bit of silver impurity can cause blue emission in ZnS phosphors, but so can other activators, so I don't think that question has been settled yet for Sterling Hill sphalerites. In any event, the combination of blue and orange emission is what your eyes see as pink. I once measured the emission spectra of a SH sphalerite like yours and documented that the orange emission strengthened and the blue emission weakened as I changed the wavelength of the UV light. You are seeing that as well."

Originally posted by Fire Viper on Nature's Rainbows in 2018.