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.

Geology
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 56 °F (13 °C) constantly.

Museum
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."

Franklin Mine Mill Site (from mindat.org)
"This is not a mineral occurrence locality. It is now the site of an apartment complex for senior citizens built in 2007. All material formerly on this dump has been mechanically sieved and removed and put in a special area at the Franklin Mineral Museum. This is an excellent example of conservatory co-operation between a construction company and the Franklin Mineral Museum.

This locality was a mineral dump near the end of Mill Street and abutting the ore railroad tracks entering theformer Palmer #2 Mill. The "Mill Site dump" was known for many years previous to the apartment building construction and supervised field trips were permitted in the mid-1980s. During the construction of the apartment building, the dump was sieved using a 5 x 5 cm grid shaker and all of the mineral specimens of "usable" size were trucked to the Franklin Mineral Museum property, where these minerals are now being added to the collecting site where museum members and visitors are receiving controlled access to the minerals, thus ensuring that fresh minerals are available to mineral collectors and by extension adding to the long-term vitality of the Franklin Mineral Museum's facilities.

The historical lore of the Mill Site Dump is that the final approach to the Palmer #2 Mill (built in 1898) was over a trestle about 8-12 meters from the rails to ground level. Allegedly, the trestle shifted and was perceived as unstable and management ordered a rapid dumping of rock to bring the fill level up to the railroad tracks and thus avert a long term mill shutdown. Lore further suggests that the ore picking table in the Mill was reversed so that any rock in the Mill was diverted back to the trestle supports. Further shipments of blasted rock of all kinds, both dump-grade and ore-grade, were taken from the Parker Shaft and elsewhere to fill the entire depression up to track level. The presence of margarosanite, hardystonite, and other desirable species that have been recovered from Mill Site rock supports the folklore."