New Jersey


Alt text Geologic processes concentrated great mineral wealth in the Franklin-Sterling Hill area over one billion years ago. Zinc mining activities in the area took place primarily on Mine Hill in Franklin and Sterling Hill in Ogdensburg.

Although the Franklin-Sterling Hill area is best known for its great zinc deposits, the early mining in this area was for iron. The use of local iron spanned well over 200 years, first by mining magnetite ores from the 1740s to 1882 to make iron metal, and secondly, by using the iron component of the zinc ores to make an alloy, spiegeleisen (German: mirror iron), from approximately 1870 to the 1960s. Iron was thus a much more important metal in the local mining history than is generally recognized.

The iron ore magnetite was exposed at the surface in full view. Development of mining shafts could be made directly in ore, so that the development of the mine was a directly paying endeavor, unlike many mines where useless, barren rock of no commercial value had to be removed at great cost just to expose the ore.

Zinc mining in Franklin was a large, strenuous, robust, dynamic and diverse activity. Zinc mining was the economic engine that powered the local economy to great strength from 1850 to 1954, sharing the responsibility with iron until iron mining activities tapered off in the early 1880's and then taking its permanent place as the dominant industry.

The Franklin-Sterling Hill mining district represents two centuries of American mining history and technology, mining law and earth sciences. It was not until after the perfection of ore-dressing techniques in the early 1800's that mining the deposits became economically feasible.

Eventually, the New Jersey Zinc Company consolidated the mines and smelters in the area. The Franklin mines became one of the few billion-dollar producing mines in the world and the ore was of exceptional quality.

The ore mined in the district was primarily zinc ore. This ore consisted of the minerals known as zincite, a zinc oxide, willemite, a zinc silicate and franklinite, a zinc iron manganese oxide.

These three minerals are very rich in zinc and are just a few of the 345+ minerals found in the district. This is about 10 percent of all those known and constitute a world record for the number of mineral species from a single locality. Yet zincite and franklinite are mined nowhere else outside the district. Willemite is found in very limited quantities scattered around the globe.

When the Franklin Mine closed in 1954, the miners were offered jobs working at Sterling Hill. The Sterling Mine temporally closed in 1958, reopened in 1961. By 1966 the mine was delivering 19,000 tons of ore per month to the smelter in Palmerton, Pennsylvania. When the Sterling Hill Mine closed in 1986, it meant the end of all underground mining in the state of New Jersey.

Sterling Hill also hosted a nonmining activity. In the mid-1960's, the Lamont-Doherty Geological Observatory operated a seismograph observatory on the 1850 level of the mine, over the north orebody. It was part of the Worldwide Standardized Seismograph Network. The seismograph facility covered an area of approximately 6000 square feet and consisted of three heat fused-quartz tubes, each 200 feet long, and a 50-foot tall vertical strainmeter, together with much instrumentation.

The history of mining at Franklin and Sterling Hill was concurrent with the development and history of the fields of mineralogy, economic geology, mining, paint manufacturing and zinc manufacturing, as well as the history of New Jersey as a state and the United States as a nation. They all grew up together.