Named stone

Upper Mercer flint

Also called Coshocton flint, Coshocton Black, Coshocton Gray, Nellie, Upper Mercer chert

Upper Mercer flintChert (and flint)Midwest/Ohio Valley

2 photos

Description

Upper Mercer flint is Ohio's main dark flint, a black to dark gray stone from a bed in the Pennsylvanian Upper Mercer limestone. In central Ohio, around Coshocton, Perry, Hocking, Muskingum and Licking counties, the horizon is a black flint in beds up to about 15 cm thick, often with lighter mottles and veins of white-blue chalcedony. Good stone is vitreous and lustrous and breaks with a deep conchoidal fracture, though it often has small cavities and a network of fine cracks. The state survey notes it looks much like Zaleski flint, which has fewer cavities and a slightly browner, more resinous look. Upper Mercer chert was carried to Michigan's Saginaw Valley in the Early Archaic and again late in the Middle Woodland.

How to identify it

Colour: Typically black (Munsell N2) to dark gray, often coal-black from carbon; lighter mottles and veins of white-blue chalcedony are common (Boulanger; Stout and Schoenlaub).
Texture: Very dense and solid, except for small irregular cavities scattered through the mass; the flint beds are cut by joints and shattered by fine cracks near the surface (Stout and Schoenlaub).
Luster: The purer material is vitreous, brittle and lustrous.
Inclusions: Veins of white-blue chalcedony and lighter mottles; small cavities.

Geology

Pennsylvanian Upper Mercer Limestone member (Pottsville Formation), which crosses Ohio from Columbiana and Mahoning counties in the east to Scioto and Lawrence counties on the Ohio River. In the north it is hard blue limestone with or without flint nodules, in Coshocton, Muskingum, Licking, Perry and Hocking counties it is a black flint, sometimes with lenses of gray flint or thin iron ore above, and in the south it becomes iron ore with little flint. The flint occurs in beds up to 15 cm thick in a limestone and shale matrix.

Where it comes from

Midwest/Ohio Valley

States

Ohio

Quarries and outcrops

Coshocton, Hocking and Perry counties, Ohio (best-known outcrops)
Muskingum and Licking counties, Ohio (black flint horizon)

Used by

Early Archaic: exotic Upper Mercer chert from east-central Ohio is common at Saginaw Valley, Michigan, sites (Castle Museum)
Middle Woodland, late: Upper Mercer chert, usually as corner-notched Jack's Reef points, increased in the Saginaw Valley before trade faded about A.D. 1,000 (Castle Museum)
Ohio Native Americans quarried Upper Mercer flint in Coshocton, Hocking and Perry counties, as well as Zaleski and Flint Ridge flint (Getz; Stout and Schoenlaub)

Look-alikes

Stones that are easy to confuse with Upper Mercer flint.

Zaleski flint: very similar, but freer of cavities, slightly deeper brown and more resinous in luster (Stout and Schoenlaub)
Holland Dark Phase (Ferdinand) chert of Indiana: macroscopically similar to Upper Mercer, according to Cantin (cited by Boulanger)
Other black Ohio flints

Sources

Boulanger, Matthew T. 2022. Neutron Activation Analysis and X-ray Fluorescence of Chert Artifacts from Mielke #1 (33SH26), Shelby County, Ohio. Supplementary Text S1, Midcontinental Journal of Archaeology.midwestarchaeology.org (opens in a new tab)
Stout, W. E., and R. A. Schoenlaub. 1945. The Occurrence of Flint in Ohio. Ohio Geological Survey, Fourth Series, Bulletin 46. Ohio Department of Natural Resources.dam.assets.ohio.gov (opens in a new tab)
Getz, Garry L. 2016 (rev.). Flint: Ohio's Official Gemstone. Educational Leaflet No. 6. Ohio Department of Natural Resources, Division of Geological Survey.dam.assets.ohio.gov (opens in a new tab)
Castle Museum of Saginaw County. Saginaw Valley Archaeology.castlemuseum.org (opens in a new tab)

Points made from this stone

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