Above: Willemite in Tephroite - Sterling Hill, Ogdensburg, New Jersey.
Tephroite does not fluoresce, but the willemite shows up as striking patterns of green lines.
The willemite / tephroite assemblage is a sort of brown to pale reddish-brown in normal light.
Sterling Hill zinc mine ceased operation in 1986,
after having produced rich zinc ore for more than seventy years. The
Hauck brothers acquired much of the Sterling Hill property around 1989,
and they opened up the Sterling Hill Mining Museum in 1990. For
collectors, they created the "Mine Run Dump" by bringing tons of ore
and rock from the mine and surrounding property. They acted just in
the nick of time to save many specimens from being lost to the rising
Mine Run is open the last Sunday of each month except January and February (I'm pretty sure December too, make sure you call ahead!). There is a poundage fee; last I checked it was $1.50 / lb. You can find some nice stuff there. There are large amounts of willemite, calcite, and franklinite, with zincite and smaller amounts of many other interesting minerals. I have found andradite, tephroite, diopside ("zinc-schefferite"), "jeffersonite", friedelite, hydrozincite, aragonite, cerussite, galena, biotite, rhodonite, schorl, sussexite, scapolite, serpentine, and several others. Don't forget the World Minerals pile; the possibilities there are endless.
The largest, best franklinite crystals I've ever found have come from Sterling Hill. The same goes for willemite. There are some rocks where, if you're patient, you can work out franklinite crystals of 1/2 to 1 cm diameter. That may be small in comparison to what used to come out of the mine itself, but such jumbo franklinites have disappeared into collections and now command very high prices. By today's standards a 1 cm franklinite crystal is a great find.
I also found a fairly large gahnite crystal back in the pits; as I recall it was about 1.5 cm across. There have also been willemite crystals 2, 3, even 4 cm across; these, too, have been found in the pits in recent years.
The collecting areas, including the Mine Run Dump, do not allow anyone younger than 13. Since there are no throngs of screaming kids, the place is usually pretty quiet. If your child is really serious about minerals but is not old enough to go to Mine Run, you can still take him / her to the Buckwheat Dump in Franklin instead.
When the museum has scheduled digs, they open up the Mine Run Dump, the Passaic and Noble Pits and the Fill Quarry to collectors. There is a lot of great collecting to be done in these places.
As with the Buckwheat dump at Franklin, there
are plenty of micromineral specimens to be found at Sterling Hill. If
you are a micromounter, this place could keep you busy forever. The
willemite / calcite / franklinite ore rocks sometimes contain cavities of
tiny, fibrous or radiating white crystals which appear "puffy", like cotton.
I don't know for sure what this stuff is, but it might be chlorophoenicite.
I have also heard brandtite mentioned as a possibility by one or two other
collectors, but I can't verify this right now. Some of the specimens
of fibrous crystals do prove to be willemite (they fluoresce bright
The dark, weathered rock from the Noble Pit often contains vugs and cavities that have tiny crystals. Again, there's an opportunity for good collecting. There can be azurite, cerussite, malachite, chlorophoenicite, aragonite, fluorapatite, franklinite, magnetite, and quite a few others in there. I once found a specimen of galena in the Passaic Pit that contained a couple of tiny, red-orange crystals of mimetite. I have never before or since found another like it, though I'm sure it must be there. Perhaps you will find it.