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.
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