Picopharmacolite

Delicate acicular sprays of white picopharmacolite can be found in spots across the surface of a small bit of calcite matrix. Under ultraviolet light the specimen becomes especially attractive: the picopharmacolite fluoresces a soft white while the underlying calcite glows a vivid orange. The piece is best appreciated under magnification, where you can also see tiny specks of löllingite on the surface, an association that reflects the arsenic-rich mineralization of the deposit.

The specimen comes from the famous Sterling Mine, Sterling Hill orebody, Ogdensburg, New Jersey, formerly operated by the New Jersey Zinc Company. Although prospecting in the district began much earlier, major mining operations started around 1870. As development progressed the mine extended far beneath Sterling Hill, eventually reaching depths of about 2,670 feet beneath the Wallkill River Valley. The complex ore system, consisting of folded “red” and “black” ores, included significant arsenic-bearing löllingite, which during later hydrothermal alteration likely provided the arsenic source for many of the district’s secondary arsenate minerals such as picopharmacolite.