Salisbury Mine (Old Hill Mine; Ore Hill Mine), Salisbury District, Salisbury, Litchfield Co., Connecticut, USA
|Latitude & Longitude (WGS84):||41° 57' 23'' North , 73° 28' 19'' West|
|Latitude & Longitude (decimal):||41.95639,-73.47194|
|Köppen climate type:||Dfb : Warm-summer humid continental climate|
The largest and most important mine in the Salisbury District. While specimens of goethite are often just labeled "Salisbury" and could be from any of the district's mines, they are most likely from the Salisbury mine because it operated into the early 20th century, and the dumps were accessible for decades afterward. According to Hiller (1967), in the 1960s the area was owned by Calvin Flint, who would show collectors the best areas, which were on the west side of the now flooded pit (Ore Hill Pond). The pond is now surrounded by residential development.
Goethite iron ore was discovered on Old Hill (later Ore Hill) in 1732, production was sporadic until 1884, then worked heavily until 1904, with 200 miners pulling out 5,000 tons per year. It was the last goethite mine to close in 1923. This mine became the most important of the several goethite mines in the state, which exploited a metamorphosed lateritic soil horizon that formed on an unconformity between the Cambro-Ordovician Stockbridge Marble and the overlying Ordovician Walloomsac Schist. The ore was typically referred to in contemporary literature as "brown hematite", "brown oxide of iron" or "limonite", none of which is strictly correct. In this area the ore body is 65 feet thick and 0.75 miles long and dips 45 north. Mostly mined as an open pit, but there were inclined shafts down to 800 feet with extensive underground workings.
Hobbs (1907) gives this description:
6 valid minerals. 4 erroneous literature entries.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Ordovician - Neoproterozoic|
443.8 - 1000 Ma
|Precambrian-Phanerozoic sedimentary rocks|
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
458.4 - 470 Ma
Age: Middle Ordovician (458.4 - 470 Ma)
Stratigraphic Name: Walloomsac Schist
Description: Black to dark-or silvery-gray, rarely layered schist or phyllite, composed of quartz, albite, and commonly garnet and staurolite or sillimanite (locally strongly retrograded to chlorite and muscovite). Locally feldspathic or calcareous near the base.
Comments: Part of Western Uplands; Proto-North American (Continental) Terrane - Carbonate Shelf
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.