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Cornwall Mines (Cornwall Iron Mine), Cornwall Borough (Cornwall), Lebanon Co., Pennsylvania, USA

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Latitude & Longitude (WGS84): 40° 16' 0'' North , 76° 23' 60'' West
Latitude & Longitude (decimal): 40.2666666667, -76.4


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.

Mineral List


68 valid minerals. 1 erroneous literature entry.

The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Genth, F. A. (1874), Second Geological survey of Pennsylvania: 1874 Preliminary Report on the Mineralogy of Pennsylvania: B.105.

Gordon, Samuel G. (1922), Mineralogy of Pennsylvania: 147.

Berkey, C.P. (1933), Mineral Deposits of New Jersey & Eastern Pennsylvania; XVI International Geological Congress Guidebook 8, Excursion A-8.

Rocks & Minerals (1938): 13: 213.

Weber, J. and Greer, R. (1965), Dehydration of Serpentine, American Mineralogist: 50: 450-464.

Lapham, D. M. (1968) Triassic Magnetite and Diabase at Cornwall, Pennsylvania in Graton-Sates Volume 1, Ore Deposite of the United States 1933-1967, p. 72-94.

Smith, II R. C. (1973) Geochemistry of Triassic Diabase from Southeastern Pennsylvania.

Reed, Juliet C. (1976), Annotated Bibliography of Minerals New to the Pennsylvania List 1965-1974, The Mineralogical Society of Pennsylvania, Inc.: 51-52.

Rose, A. W., Herrick, D. C. and Peter Deines (1985) An oxygen and sulfur isotope study of skarn-type magnetite deposits of the Cornwall type, southeastern Pennsylvania, Economic Geology: 80: 418-443.

Smith, II, R. C., Berkheiser, S. W. Jr. and D. T. Hoff (1988) Locations and analyses of selected Early Nesozoic Copper Occurrences in Pennsylvania in Studies of the Early Mesozoic Basins of the Eastern United States, USGS Bulletin 1776, p. 320-332.

Anthony, Bideaux, Bladh, Nichols: "Handbook of Mineralogy", Vol. 1 (1990) (tochilinite).

Tschernich, R. (1992): Zeolites of the World: 70.

Leet, Milt (2004), The Tumbler - Zeolites and Their Associations (September): 4.

Kearns, L.E. & Kearns, C.A. (2008), Mineral News: 24(1): 8-9.

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