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Ore Hill Mine (Warren Silver-Lead Mine; Warren Zinc Mine), Warren, Grafton Co., New Hampshire, USA

Tremolite
Ore Hill Mine, Warren, Grafton Co., New Hampshire, USA

Photo: 2007 Peter Cristofono
Massive sulfide deposit, discovered by True Merrill, the landowner, in 1834. The deposit was mined intermittently until ca. 1915 for lead, copper, zinc and silver. The major period of mining was from 1889-1893 when the mine was operated by the Warren Zinc Company.

This site is located within the White Mountain National Forest, and the U.S. Forest Service has undertaken a reclamation project on the main dumps, which have been graded, loamed and seeded in order to try to slow down the leaching of metals into the small stream which passes along the foot of the dumps. Digging to collect is no longer allowed on these dumps.

Secord and Brown (1986) reported: "Examination of the unique lithologies of the Ammonoosuc Volcanics at the Ore Hill mine (i.e., a basal, pillowed, epidotized amphibolite, a cordierite-kyanite footwall schist, a muscovite schist host rock, and a tremolite-phlogopite cap rock) suggests that the sequence represents a deformed and metamorphosed alteration zone associated with sea-floor precipitation of massive ore. The essentially stratiform and strata-bound nature of the Zn-Pb-Cu orebody suggests syngenetic massive sulfide genesis. Based on mining records, a reverse ore zonation is documented, in which chalcopyrite appears to be concentrated in the upper sections of the orebody, and sphalerite and galena increase toward the base. Evidence is presented, however, to support a lateral as opposed to a vertical metallic zonation scheme. Major element trends, associated with alteration in footwall mafic metavolcanic rocks (SiO2, FeO, MgO, Na2O, and K2O depletions), suggest sea-floor metasomatism of the local mine sequence..."

Mineral List

Anthophyllite
'Apatite'
'Biotite'
Bornite ?
Chalcopyrite
'Chlorite Group'
Cordierite
Epidote
Galena
'Garnet'
Hematite
'Hornblende'
Kyanite
'Limonite'
Malachite
Muscovite
Phlogopite
Pyrite
Pyrrhotite
Quartz
Rutile
Spessartine
Sphalerite
Talc
Tremolite
Vesuvianite
Zoisite


27 entries listed. 21 valid minerals.

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References

Hitchcock, Charles H. (1869): First Annual Report upon the Geology and Mineralogy of the State of New Hampshire.

Little, William (1870) History of Warren, pp.449-450.

Fowler-Billings & Page (1942), The Geology of the Cardigan and Rumney Quadrangles - New Hampshire.

Bannerman, Harold M. (1962): Ore Hill Zinc Mine, Warren, New Hampshire (New Hampshire State Planning and Development Commission)

Secord, Theresa K. and Brown, Philip E. (1986). Geology and geochemistry of the Ore Hill Zn-Pb-Cu massive sulfide deposit, Warren, New Hampshire (Economic Geology; April 1986: 81(2): 371-387.

Rocks & Minerals (2005), New Hampshire Mineral Locality Index: 80: 242-261.

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