Cornwall Mines (Cornwall Iron Mine), Cornwall Borough (Cornwall), Lebanon Co., Pennsylvania, USA
|Latitude & Longitude (WGS84):||40° 16' 0'' North , 76° 23' 60'' West|
|Latitude & Longitude (decimal):||40.26667,-76.40000|
|Köppen climate type:||Cfa : Humid subtropical climate|
Originally, a series of three open pit mines (Big Hill, Middle Hill, Grassy Hill) with underground openings, located at Cornwall, near Lebanon. Started in 1732 and owned by the Cornwall Ore Banks Company (1864) and later, the Bethlehem Steel Company.
Lapham (1973, including Plate 22) notes that in the 20th century, 2 major deposits were being worked: the western by the open pit and underground No. 3 mine, and the eastern by the No. 4 mine. Much of the operation came to an abrupt halt in June 1972 when floods from Hurricane Agnes flooded the underground mines. Neither underground operation was reopened.
Smith et al. (1988) note that more copper-, cobalt-, and possibly gold-rich ore with substantial byproduct iron was actively pursued from the eastern end of the open pit until June 30, 1973. The smaller, footwall ore body beneath the eastern end of the open pit was never mined, but may contain as much as 0.006 ounce/ton Au. The ore bodies consisted of replacement of contact metamorphic scarn by slightly later copper and iron-bearing hydrothermal fluids. The ore-bearing fluids may have been derived in part from the Triassic, York Haven Diabase, which forms the footwall to the larger ore bodies (Rose et al. 1985). Certainly, the diabase served for the heat engine.
Smith et al. (1988) report that the total ore production known is 106,000,000 tons of recovered ore with an apparent greade of 0.4 % copper. From 1908 to 1973, the period for which records could be found, 67,000 ounces of gold were recovered and 443,000 ounces silver. Recovered pyrite concentrates contained 1.1 % Co and 0.1 % Ni. This is the type "Cornwall Type" iron ore deposit.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
68 valid minerals. 1 erroneous literature entry.
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.
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201.3 - 252.17 Ma
|Mesozoic intrusive rocks|
Age: Triassic (201.3 - 252.17 Ma)
Lithology: Intrusive igneous 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. 
443.8 - 485.4 Ma
|Hamburg sequence rocks|
Age: Ordovician (443.8 - 485.4 Ma)
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.