Hill and Franklin Zinc Mines
wikipedia ..."The Sterling Hill Mine, now known as
the Sterling Hill Mine Tour & Museum of
Fluorescence, is a former iron and zinc mine in
Ogdensburg, Sussex County, New Jersey, United
States. It was the last working underground mine in
New Jersey when it closed in 1986, and it became a
museum in 1989. Along with the nearby Franklin Mine,
it is known for its variety of minerals, especially
the fluorescent varieties. It was added to the
National Register of Historic Places in 1991.
began at the site in the 1630s, when it was
mistakenly thought to be a copper deposit. George
III of the United Kingdom granted the property to
William Alexander, titled Lord Stirling. Stirling
sold it to Robert Ogden in 1765. It went through
several owners until the various mines were combined
into the New Jersey Zinc Company in 1897. The mine
closed in 1986 due to a tax dispute with the town,
which foreclosed for back taxes in 1989 and
auctioned the property to Richard and Robert Hauck
for $750,000. It opened as a museum in August 1990.
Franklin Furnace, also known as the Franklin Mine,
is a famous mineral location for rare zinc, iron,
manganese minerals in old mines in Franklin, New
Jersey, United States. This locale produced more
species of minerals (over 300) and more different
fluorescent minerals than any other location. The
mineral association (assemblage) from Franklin
includes willemite, zincite and franklinite.
the mid-to-late 19th century the furnace was the
center of a large iron making operation. Russian,
Chilean, British, Irish, Hungarian and Polish
immigrants came to Franklin to work in the mines,
and the population of Franklin swelled from 500 (in
1897) to over 3,000 (in 1913).
Furnace mine which was adjacent to the actual
furnace, was a 120+ foot vertical shaft just under
Franklin Falls. Other rare minerals include
esperite, clinohedrite, hardystonite, and others.
There are scores of minerals found only here, such
as johnbaumite (an arsenous apatite), mcgovernite,
etc. Sterling Hill, a very similar zinc orebody, is
located a few miles away in Ogdensburg.
The ore bodies at the
Sterling Hill mine lie within a formation called the
Reading Prong massif; the ores are contained within
the Franklin Marble. This was deposited as limestone
in a Precambrian oceanic rift trough. It
subsequently underwent extensive metamorphosis
during the Grenville orogeny, approximately 1.15
billion years ago. Uplift and erosion during the
late Mesozoic and the Tertiary exposed the ore
bodies at the surface; the glaciers of the
Pleistocene strewed trains of ore-bearing boulders
for miles to the south, in places creating deposits
large enough to be worked profitably.
the area of the Franklin and Sterling Hill mines,
357 types of minerals are known to occur; these make
up approximately 10% of the minerals known to
science. Thirty-five of these minerals have not been
found anywhere else. Ninety-one of the minerals
fluoresce. There are 35 miles (56 km) of tunnels in
the mine, going down to 2,065 feet (629 m) below the
surface on the main shaft and 2,675 feet (815 m) on
the lower shaft. As of 2017, other than the very top
level of the mine (<100 ft), the entire lower
section has been flooded due to underground water
table and hence no longer accessible. The mine
remains at 56 °F (13 °C) constantly.
tour spends about 30 minutes inside the Exhibit hall
which contains a wide variety of mining memorabilia,
mineralogical samples, fossils, and meteorites. It
then leads into the mine for a 1,300 feet (400 m)
walk on level ground through the underground mine.
The walk goes through a new 240 feet (73 m) section
called the Rainbow tunnel which they blasted in 1990
using 49 blasts and at a cost of $2 a foot. In the
Rainbow room, short wave UV lights are turned on to
demonstrate the entire tunnel and various samples
glowing with fluorescence. The mine is also home to
the Ellis Astronomical Observatory, the Thomas S.
Warren Museum of Fluorescence, and a collection of
The museum periodically arranges public mineral
collecting sessions as well as more private and
behind the scene events for local geology clubs."