Sterling Hill Zinc Mine - most fluorescent minerals in one place on earth



Sterling  Hill and Franklin Zinc Mines
from 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.

Mining  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,[1] 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.

During  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).

The  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.

In  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.[9] 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 56F (13C) constantly.

The  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  mining equipment.
The museum periodically arranges public mineral  collecting sessions as well as more private and  behind the scene events for local geology clubs."