Inquiry, Journey, Discovery: Mineralogy at Sterling Hill

This is the first of three pieces about the Sterling Hill Mining Museum. This article focuses on the mineral collection. The next post will explore the history of the mine, and the final installment will explain what visitors can expect to find at the museum today.

I am fortunate to be married to someone who shares my enthusiasm for science. This year, my wife and I spent a weekend at the Sterling Hill Mining Museum in Ogdensburg, NJ for our two-year anniversary.

The museum is located on the grounds of what was formerly one of the most productive zinc mines in the state. It is also the “world capital” of fluorescent minerals – the area has produced over 80 varieties, and others may still be buried, undiscovered, in sections of the hillsides.

When operation costs drove the mine out of business in the 1980's, it was converted into a center for education about history and science. The primary focus is on geology and mineralogy, but there are displays to teach visitors about such things as chemistry, and the Ellis Astronomical Observatory also makes its home on the property.

In addition to minerals from the local mines, Sterling Hill hosts a huge collection of rare and interesting minerals from all over the world, many of them fluorescent.

On Friday night, we were treated to a tour of the mines by longtime museum volunteer Bill Kroth, followed by a session at the telescope he runs. On Saturday, we again visited the museum.

Willemite (Zn2SiO4) is the most common fluorescent mineral found in the Sterling Hill mine. Indeed, the predominance of this form of zinc silicate ore makes the Franklin and Sterling Hill mines unique.

A large sheet of willemite (green) with fluorescent calcite (red) from the mine.

A slab of sphalerite (ZnS), garnet and hornblende found 900 feet below ground in the Sterling Hill mine. Sphalerite is one of the main precursors of willemite. It is transformed through one of two means: by oxidation in a siliceous (silicon-rich) environment, or by alteration from hydrothermal veins. New Jersey's willemite was made via the latter process.

Willemite lining the walls of the mine.

Scheelite (CaWO4) from Trumbull, CT. The fluorescence is due to tungstate ions.

Meionite (Ca4Al6Si6O24(CO3)) from Grenville, Quebec. It fluoresces yellow in short-wave ultraviolet (UV) light, and red in long-wave UV light.

One of several unusual malachite (Cu2(CO3)(OH)2) samples. This piece originated from Lubumbashi in the Haut-Katanga Province of the Democratic Republic of Congo. The area is known for its copper, in which malachite typically forms.