FLINT
OHIO'S OFFICIAL GEMSTONE
  
Ohio flint is known to rock and mineral collectors throughout the country for its brilliant colors and its suitability for crafting into beautiful jewelry. It was appropriate, therefore, that in 1965 the Ohio General Assembly named flint Ohio's official gemstone.

Flint, a variety of quartz, is a hard, durable rock that is composed of silicon dioxide (SiO2), or silica. Minor amounts of chemical impurities commonly impart a wide variety of colors to flint, in shades of red, pink, green, blue, yellow, gray, white, and black, which may be intricately intermingled. Its color, hardness, and ability to take a high polish make Ohio flint a coveted item among lapidarists, who produce unique jewelry items from this rock.


ARCHAIC KNIFE FORM
  
Flint (and its impure form, chert) is widely distributed in Ohio in rocks of Silurian (438 to 408 million years ago), Devonian (408 to 360 million years ago), and Pennsylvanian (320 to 286 million years ago) age. These rocks were deposited in shallow, tropical seas that covered the area that is now Ohio during the Paleozoic Era. Most flint deposits are associated with marine limestones, and it is thought that the silica necessary to form flint was derived from the siliceous spicules that formed the skeletal support for sponges that lived in the seas.

The most famous deposit of flint in Ohio is an area in eastern Licking and western Muskingum Counties known as Flint Ridge. The Vanport flint of Pennsylvanian age covers a ridgetop area of about 6 square miles. The flint deposit ranges in thickness from about 1 foot to 12 feet.
ARCHAIC DOVETAILS
  
Flint Ridge flint is noted for its array of colors and suitability for jewelry making and for its long and widespread use by American Indians. Hundreds of pits dotting Flint Ridge are evidence of the extensive quarrying of flint by a succession of American Indian cultures. The earliest peoples to use this raw material for various tools, including knives, scrapers, and projectile points, were the Paleo-Indians, a culture that was contemporaneous with the last phases of the Pleistocene Ice Age and extinct animals such as mastodon and mammoth that roamed the area until about 10,000 years ago.

It is thought that American Indians from throughout the Midwest made periodic pilgrimages to Flint Ridge in order to obtain a supply of flint for tool making. The purity of this deposit permitted these skilled workers to fashion a wide variety of tools, weapons, and ceremonial pieces. Artifacts made from Flint Ridge Flint have been found as far east as the Atlantic coast, as far west as Kansas City, and as far south as Louisiana.
CORES FROM WHICH DELICATE
KNIVES WERE STRUCK
  
Ohio's first peoples also quarried flint from deposits other than Flint Ridge. Most notable are the Zaleski flint in Vinton and Jackson Counties and the Upper Mercer flint in Coshocton, Hocking, and Perry Counties. These units are of Pennsylvanian age. Other flint deposits of Silurian, Devonian, and Pennsylvanian age were also utilized in a minor way.

Flint was important to early European settlers in Ohio. These pioneers used impure, prous deposits of flint for buhrstones to sharpen tools and grind grain. In addition, flint was used in flintlock rifles and to start fires.

In 1933 the Ohio Historical Society established Flint Ridge State Memorial on a 525-acre portion of Flint Ridge. This area contains numerous pits dug by American Indians to obtain flint. In 1968 a museum was operated by the Ohio Historical Society, contains displays on the geology and use of flint. Trails through the memorial site pass by numerous ancient quarry pits. Flint Ridge State Memorial is located 4 miles north of Interstate 70 (exit 141 at Brownsville) on Licking County Road 668. The museum is open Wednesday through Sunday from Memorial Day through Labor Day and on Weekends from Labor Day through October.

  
  
FURTHER READING
  • Carlson, E.H., 1991, Minerals of Ohio: Ohio Division of Geological Survey Bulletin 69, 155 p.
  • DeLong, R. M., 1972, Bedrock Geology of the Flint Ridge Area, Licking and Muskingum Counties, Ohio: Ohio Division of Geological Survey Report of Investigations 84, color map with text.
  • Mills, W. C., 1921, Flint Ridge: Ohio Archaeological and Historical Society Quarterly, v. 30, p. 90-161.
  • Stout, W. E., and Schoenlaub, R. A., 1945, The Occurrence of Flint in Ohio: Ohio Division of Geological Survey Bulletin 46, 110 p.