The state of Ohio provides a treasure trove of rocks and fossils, especially along the coastline of Lake Erie, the fourth largest lake in the US.
Some of the rocks in the lake’s basin date back 400 million years, so you could make a geologically significant find there.
Read on to learn the 16 most common types of rocks and fossils found in Ohio, where to find them, and what they typically look like.
Types of Rocks Found in Ohio
The information provided in this article by YesDirt.com is for informational purposes and is subject to change. Laws are updated. Accessibility guidelines and restrictions change. Be sure to confirm the land status and collection rules before you travel to an unfamiliar location or collect any material.
You might think of this stone in relationship to Michigan since there’s a city named Flint, but we’re starting with the Ohio state rock.
You’ll find Lake Erie chock full of flint.
A common material in Native American hunting knives, its colors range from black and dark blue to green with some red flint.
Flint’s smoothness and the consistency of shape make it easy to spot but handle it carefully because the fragile rock breaks easily.
Start your search in the aptly named Flint Ridge, Ohio, focusing on the marine limestone deposits on the south shore of Lake Erie.
Brachiopods also populate this area.
These ancient relatives of clams lived during the Paleozoic era.
You can find their fossilized remains in the ancient seabeds.
Look for something that resembles a sea shell but with an asymmetrical pattern and a dull gray color. These items typically date to 550 million years.
In northwestern Ohio, explore the fissures and veins in large rocks.
These calcium carbonate rocks often appear in central and western Ohio.
Also, check formations of silurian dolomites in the northwestern area of the state.
You can find the calcite as large crystal clusters that range in color from clear to gold to dark brown.
Look for celestite formations on South Bass Island, Ohio.
Explore The Crystal Cave in Put-In-Bay.
Discovered in 1897, it features a plethora of celestite in whites and pale blues.
You can also find celestite in the northwestern part of the state where it formed in the dolomitic limestone.
The carbonate mineral dolomite appears a dingy white in the shape of a saddle.
Comprised largely of calcium magnesium carbonate, they also appear as dolostones.
You can find these along the banks of Lake Erie where it meets the Hudson River.
Another mineral you can easily find in the state’s northwest corner, fluorite, comes in a cubic shape.
Comprised of fluorine crystals, impurities often provide the mineral formations with the colors of the rainbow.
These may appear streaked like marble or like a tie-dyed shirt.
In other cases, they develop in a single color, such as deep emerald green.
Lake Erie provides a hotbed of igneous rock types. Igneous rocks form when hot magma quickly cools, then hardens.
This volcanic activity took place during the Precambrian period, so when you explore central or eastern Ohio along the shores of Lake Erie, some of the granite you find dates to 800 to 900 million years ago.
Granite can contain alkali feldspar, quartz, and plagioclase, and appears in clear, black, white, or red.
Gypsum gets confused with salt or halite because of its dull white color.
Sometimes it develops clear and resembles a crystal formation of calcium sulfate.
Look in the western area of Lake Erie, in glacial lake beds and evaporated water beds.
You can also find these in north-eastern and central Ohio.
They develop into small tubular formations or large formations.
See also: Can Gypsum Scratch Glass?
Honeycomb coral develops as a uniquely shaped sedimentary rock comprised of closely packed corallites.
Explore the shores of Lake Erie for this coral formation.
The sedimentary rock limestone often appears in nature with ancient fossils.
Comprised of calcium carbonate, it develops in warm, inland seas.
In the Paleozoic era, Ohio formed the sea bed of just such a sea.
Typically white or another light color, you can find ancient marine life embedded in them.
Look in western Ohio.
You can find naturally polished Petoskey stones with embedded fossils in them, too.
They usually formed from fossilized rugose coral during the Great Lake’s glacial formation.
These stones appear to have a white spider-web wrapped around the rock.
The igneous rock type rhyolite provides a granite-like substance that’s finer in composition and structure.
Although porous, it is also of one texture.
In western Ohio, on Lake Erie, you can find this among the Precambrian rocks.
You can’t miss its fine-coarse crystals containing plagioclase, quartz, and sanidine.
It comes in a bevy of colors including green, black, orange, and gold.
Start your search in eastern Ohio looking at the Devonian, Pennsylvanian, Permian, and Mississippi era formations.
The sedimentary rock sandstone proves easy to find since Amherst, Ohio hosts the largest sandstone quarry in the world.
Granules of many rocks combine naturally in ancient waters, then settle in the bed.
Sandstone appears tan or light brown and comprises feldspar grains, quartz, sand, and can contain other rocks or minerals, too.
The typically black shale, a clastic sedimentary rock, provides a chocolate-colored thin clay.
It may show white specks.
You can easily find this rock at the Bedford Shale outcrop by Lake Erie.
The sedimentary rock, siltstone, also called aleurolite, consists of angular silt granules.
A stronger, lighter rock than shale, it otherwise resembles it.
You can find it with shale in the Bedrock Shale formation.
Found in shale formations throughout the state, trilobite fossils prove tougher to find than brachiopods.
You can also find trilobites in limestone formations around Lake Erie.
An ancient animal of the Devonian period, these fossils date to 520 million years ago.
You will need to dig for these since they aren’t found on the ground.
You could find rarer rocks including diamonds in Ohio.
To date, six major diamond finds occurred in the state.
These occur rarely though, so don’t get your hopes up.
You might also find marcasite, a crystal structure comprised of iron sulfide.
It develops in a gold color and people often mistake it for pyrite.
Explore the formations of Devonian era Ohio Shale to find marcasite.
Exploring Ohio means exploring the bed of an ancient sea. You should check to see whether you need a free permit from the state before you collect rocks.
You should also ask for permission before collecting fossils, rocks, or minerals if you need to enter private property to search for them.
If you want to search for rocks that aren’t above ground, like trilobites, you will need rock hunting equipment.
Otherwise, you only need a bag to hold your finds.
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