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

• Display
  • Standard
  • Detailed
  • By Strunz Category
  • By Dana Category
• Photos
  • Mineral Photos (61)
  • - Full View (38)
  • - Photomicrograph (17)
  • - Stacked Photomicrograph (6)
  • Site Photos (10)
  • - Modern Site Photo (9)
  • - Historical Site Photo (1)
  • Add Photo
• Maps
  • Map Pages
  • Nearest Localities
• Search
  • Mineral Search
  • Search Google

Originally, a series of three open pit mines (Big Hill, Middle Hill, Grassy Hill) located at Cornwall, near Lebanon. Started in 1732 and owned by the Cornwall Ore Banks Co. (1864) and later, the Bethlehem Steel Co.

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 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 oz/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 oz of gold was recovered and 443,000 oz. silver. Recovered pyrite concentrates contained 1.1 % Co and 0.1 % Ni. This is the type "Cornwall Type" iron ore deposit.

Mineral List

Actinolite Albite Analcime Andalusite Andradite Anorthite var: Labradorite Anorthoclase Antigorite 'Apatite' 'Apophyllite' Apophyllite-(KOH) Aragonite Augite Azurite Baryte Bieberite 'Biotite' Botryogen Brochantite Brucite Calcite Chalcanthite

Chalcocite Chalcopyrite 'Chlorite Group' Chrysocolla Chrysotile Clinochrysotile 'Clinopyroxene Subgroup' Copper Covellite Crednerite ? Cuprite Datolite Diopside Elbaite Enstatite Epidote Erythrite Fluorite Forsterite Galena 'Garnet' 'Gmelinite' ?

Grossular Gypsum Harmotome ? Hematite 'Heulandite' 'Hornblende' 'Hypersthene' Ilmenite Kaolinite 'K Feldspar var: Adularia' Langite Laumontite Magnetite Malachite Marcasite Microcline Millerite Muscovite Natrolite 'Olivine' ? Orthoclase Phlogopite

Pigeonite Prehnite Pyrite Pyroaurite 'Pyroxene Group' Pyrrhotite Quartz Rhodochrosite ? Ruizite Rutile 'Serpentine Group' Sphalerite 'Stilbite' Talc Thomsonite-Ca Titanite Tochilinite 'Tourmaline' Tremolite Vesuvianite Wurtzite

87 entries listed. 69 valid minerals. 1 erroneous literature entry.

References