Ohio is a good state for rockhounding. Ohio is well known for its Ohio flint and its flint deposits. The state also is known for its fossils. Lesser known, however, is that Ohio is home to the largest geode in the world. Ohio also has numerous natural arches in the southern and eastern portions of the state. In addition, numerous prehistoric earthworks are located in Ohio. Southern Ohio also is home to the Serpent Mound Crater, an ancient meteorite crater.
State Rocks, Gemstones, Minerals, Fossils, & Dinosaurs
Rockhounding Tip: Knowing state rocks, gemstones, minerals, fossils, and dinosaurs often can be very useful information for rockhounders. Ordinarily, states with significant mineral deposits, valuable gemstones, fossils, or unusual or significant rock occurrences will designate an official state mineral, rock/stone, gemstone, fossil, or dinosaur to promote interest in the state’s natural resources, history, tourism, etc. Accordingly, such state symbols often are a valuable clue as to potential worthwhile rockhounding opportunities.
State Gemstone: Ohio Flint (1965)
Ohio designated Ohio flint as its official state gemstone in 1965. Flint – like chert, jasper, chalcedony, and agate - is a cryptocrystalline variety of quartz (meaning that its crystal structure is so small that it cannot be seen by the naked eye). Each of these materials can be knapped to form tools such as knives, spear points, arrowheads, and scrappers. In addition, when struck by steel, flint will produce a spark, which is why it was used in flintlock firearms and to start fires. In Ohio, large quantities of flint exist, especially in the eastern and central parts of the state. The most famous deposit of Ohio flint, the Pennsylvanian-age Vanport flint, occurs in an area of eastern Licking and western Muskingum counties known as Flint Ridge. The Vanport flint consists of laterally discontinuous meganodules of secondarily chertified limestone. This material occurs in a wide variety of colors.
State Fossil: Isotelus (1985)
Ohio designated the trilobite genus Isotelus as its official state invertebrate fossil in 1985. Isotelus is a genus of extinct marine arthropod of the class trilobite. A trilobite was an invertebrate marine creature that had a hard outer shell or skeleton. Two lines crossed the body of the trilobite, making it appear to be in three parts. Trilobite means “three-lobed creature.” Isotelus primarily lived in the shallow seas that covered Ohio during the Ordovician Age, about four hundred forty million years ago. Although over 20,000 species of trilobites are known, Isotelus was a predatory giant among its fellows, crawling along the sea floor in search of smaller creatures to feed on. Trilobites were a very successful group of arthropods during the Paleozoic Era. As arthropods -- relatives of modern insects and crabs -- they had a segmented body, jointed appendages, and a tough exoskeleton. Usually only the exoskeleton is found as a fossil, but occasional specimens of some trilobites have been found which show that underneath the shell was the body of an animal somewhat similar to a pill bug, with a pair of legs on every segment, and even antennae. Why the group died out remains a mystery, but the mass extinction at the end of the Paleozoic Era rang the death knell for over 90% of the world's species, trilobites included. A partial specimen of a large specimen of Isotelus was discovered during a geological survey of Ohio in 1837-38. A complete, 14.5-inch specimen was uncovered in 1919 during construction of the Huffman Dam near Dayton (it was donated to the Smithsonian and is on display). While the largest complete Isotelus known measures 16 inches, partial remains indicate that the largest individuals may have grown to as much as 28 inches.
State-specific rockhounding books (including the books listed here as well as other books), regional rockhounding site guides, and other helpful rockhounding resources are identified - by category - in the Books & Gear section of Gator Girl Rocks with a link to the Gator Girl Rocks Amazon Store where you may easily browse selected resources and securely place an order. Your order will benefit Charity Rocks!
The Ohio Geological Survey includes very useful educational & other resources regarding fossils, rocks, minerals, and gems. It also has produced a brochure regarding fossil collecting in Ohio with recommended sites.
A useful website focusing on Ohio minerals, including collecting sites.
- Mark J. Camp, Roadside Geology of Ohio (2006).
- June Culp Zeitner, Midwest Gem, Fossil, & Mineral Trails: Great Lakes States (Rev. ed., June 1999 – first published in 1955).
- June Culp Zeitner, Midwest Gem Trails: Field Guide for the Gem Hunter, the Mineral Collector, and the Tourist (3d. Rev. ed., 1964 – originally published in 1956).
- James Martin Monaco & Jeannette Hathway Monaco, Fee Mining & Mineral Adventures in the Eastern U.S. (2d ed. 2010).
- Kathy J. Rygle & Stephen F. Pedersen, Northeast Treasure Hunter's Gem & Mineral Guide (4th ed. 2008).
Museums of Interest to Rockhounders
of Natural History
The Cleveland Museum of Natural History is regarded as one of the finest natural history museums in North America. The Wade Gallery showcases the Museum’s spectacular collection of more than 1,500 gems and minerals. In addition, the Museum’s Kirtland Hall of Prehistoric Life exhibits a wide variety of fossils including fossil plants and invertebrate animals from the bottom of ancient oceans, the monstrous meat-cleaver jaws of Dunkleosteus terrelli (the fossil fish found in the shale around Cleveland), and dinosaurs (including “Happy,” the 70-foot-long Haplocanthosaurus delfsi, (the oldest sauropod on exhibit anywhere and the holotype of the species), and even age-age fossils including a Smilodon (a saber-tooth cat from California’s La Brea tar pits), a mammoth, and the Johnstown Mastodon (that was discovered in Ohio).
Orton Geological Museum
Ohio State University – Columbus, Ohio
The museum exhibits feature the geologic history of Ohio plus fossils and minerals from all over the world. Among the exhibits are mammoth and mastodon teeth, a full-sized replica of a Tyrannosaurus rex skull, a fluorescent mineral booth and meteorites. The centerpiece of the exhibit hall is the mounted skeleton of a giant ground sloth, one of four found in the state.
Karl E. Limper Geological Museum
Miami University – Oxford, Ohio
The museum contains hundreds of specimens of the world-famous fossils of Southwestern Ohio as well as minerals, rocks, fossils, and meteorites from all over the world.
Places to Visit - Interesting Sites To See
Flint Ridge State Memorial
Licking County, Ohio
Flint Ridge State Memorial is located on a 525-acre portion of Flint Ridge. Numerous trails through the memorial site lead visitors past hundreds of quarries dug by Native Americans to obtain flint. A museum, constructed in 1968 around a restored prehistoric quarry, includes displays on the geology and uses of flint.
Cave – the Largest Known Geode in the World
The Crystal Cave is a limestone cave located in Put-in-Bay, Ohio on South Bass Island in Lake Erie (at Heineman’s Winery). It is the largest known geode in the world. The geode is approximately 35 feet wide at its widest point. The cave was discovered in 1897 approximately forty feet below the winery. The walls are lined with large celestine crystals.
Licking County, Ohio
The Newark earthworks are geometric earthen enclosures constructed during the prehistoric time period (the Hopewell ‘Mound builders’). The site consists of three sections of preserved earthworks – the Great Circle Earthworks (about 1,200 feet in diameter), the Octagon Earthworks, and the Wright Earthworks. This complex contained the largest earthen enclosures in the world (about 3,000 acres). In 2006, Ohio designated the Newark Earthworks as its official state prehistoric monument.
Montgomery County, Ohio
Miamisburg Mound is a prehistoric Indian burial mound, believed to have been built by the Adena Culture, about 1000 BC to 200 BC. It is the largest conical burial mound in Ohio. Originally, it was nearly 70 feet tall and 877 feet in circumference. It remains virtually intact from its construction over 2,000 years ago.
Great Serpent Mound
Adams County, Ohio
Great Serpent Mound is a 1,348-foot long prehistoric earthwork over 1,300 feet long. It looks like a snake or serpent in the act of uncoiling. An oval mound near the end of the mound looks like the open mouth of the serpent. Archaeologists believe that ancient cultures built it at least a thousand of years ago.
Hocking Hills State Park – Logan, Ohio
‘Rock House’ is located in Hocking Hills State Park. Rock House is Ohio’s most unusual natural arch. It has a span of twenty feet, a clearance of forty feet and a length of 185 feet. It is the state’s largest natural arch and its longest natural tunnel. Rock House formed in eastern Ohio’s Mississippian- age Black Hand Sandstone. The park also includes other arches and caves.
Rockbridge State Nature Preserve – Rockbridge, Ohio
Rock Bridge is located in Rockbridge State Nature Preserve. Rock Bridge is Ohio’s longest natural bridge (92 feet). Rockbridge formed in eastern Ohio’s Mississippian- age Black Hand Sandstone.
South Shore of Kelleys Island in Lake Erie, Erie County, Ohio
The flat-topped limestone slab (measuring 32 feet by 21 feet) displays carvings of animals and human figures. It was discovered partly buried in the shoreline in 1833. Archaeologists believe the inscriptions date from sometime between AD 1200 and 1600.
Rockhounding Sites for Children & Families
Fossils - Ordovician
Trammel Fossil Park – Sharonville, Ohio
Located north of Cincinnati, Trammel Fossil Park is a good place to look for Ordovician fossils (fossils from about 485 - 443 million years ago) including brachiopods and bryozoans.
Fossils – Devonian
Fossil Park – Sylvania, Ohio
Fossil Park in Lucas County, Ohio is a great place to look for Devonian era fossils (fossils from about 375 million years ago) including trilobites, brachiopods, horn coral, bryozoans, and crinoids.
Fossils – Silurian
Oakes Quarry Park – Fairborn, Ohio
Oakes Quarry Park in Fairburn (near Dayton) allows some fossil collecting in designated areas within the 190 acre park. The park is a former limestone quarry and contains evidence of ice age glaciers as well as a prehistoric fossil coral reef. Fossils include brachiopods, crinoids, and other Silurian age (about 425 million years ago) marine fossils.
State Parks – Southwestern Ohio
Caesar Creek (Warren and Clinton Counties), Hueston Woods (Preble and Butler Counties), Cowan Lake (Clinton County), and Stonelick (Clermont County) State Parks allow fossil collecting; check at the ranger station for designated areas. Caesar Creek State Park requires a collecting permit (available free from the Visitors Center).