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 era 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, more than 360 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 of tunnels in the mine, going down to below the surface in the main shaft and in 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 the natural water table and hence is no longer accessible. The mine’s temperature sits at a constant . ==Museum==