Economic Mineral Resources

The category of economic mineral resources includes both industrial minerals and fossil fuels. The abundance of these resources in Ohio has had a big influence in the economic development of the state and its continued prosperity. In total, these resources have an annual value of more than 2.5 billion dollars.

Fossil Fuels


The first European settlers in Ohio recognized the presence of coal in natural outcrops in stream and river banks in the eastern part of the state. As the industrial revolution began, Ohio’s coal resources became increasingly important. One of the primary objectives of the first Geological Survey of Ohio in 1837-1838 was to survey the mineral resources of the state, particularly coal. Soon, coal was being mined as a fuel to heat homes and businesses. Development of the Ohio canal system in the 1830s and 1840s permitted easy transport of coal from mines to markets. By the mid 1800’s, railroads began to replace the canals, allowing for faster and more efficient delivery of coal to consumers. By the late 1800’s, mechanization and improvement of mining methods led to a steady increase in the production of Ohio coal. Much coal was used to make coke to fuel the many steel mills that dotted the upper Ohio River valley. Eventually, coal became the primary source of energy to generate electricity and the dominant underground mines were replaced by surface strip mines, where large amounts of overlying rock was removed by massive shovels and drag lines to get access to the valuable coal seam.

Currently, there are about 90 active coal-mining operations in 15 eastern Ohio counties that produce coal worth about $626 million annually. In recent years there has been a trend to return to underground-mining methods, particularly long-wall mining. With this technique, almost all of the coal is recovered for sale in contrast to the older room-and-pillar method where up to half the coal remained in the ground to support the roof of the mine. The leading coal-producing counties in decreasing order are Belmont, Harrison, Tuscarawas, Athens, and Jefferson. Although there are about 50 named coal beds or seams in Ohio, only a few are of sufficient thickness and extent to be mined. Most production comes from the Pittsburgh (No.8) coal seam.

Coal formed in Ohio during the Pennsylvanian Period about 300 million years ago when the state was near the equator with a warm climate. Eastern Ohio was a low-lying coastal area that was crossed by delta-building streams from the rising Appalachian Mountains to the east. Vast swamps with lush vegetation dominated the coastal areas. As the vegetation died and fell into the oxygen-poor waters of the swamps, it became thick layers of peat that eventually were compressed and buried under shale and sandstone as rivers switched course. As more rock accumulated above the swamp vegetation, it became compressed and altered first to lignite, or brown coal, and eventually to bituminous coal.

Unfortunately, most Ohio coal has about 3.5 percent sulfur, a compound that forms sulfur dioxide when the coal is burned. Most swamps in which Ohio coal formed were near the sea. Periodically, sea water flooded the swamps resulting in the formation of pyrite (iron sulfide) and other sulfur compounds. The Clean Air Act of 1970, and later amendments, caused a rapid decline in production of Ohio coal from the all-time annual high of 55 million tons in 1970. Coal-cleaning techniques to remove sulfur compounds and techniques to remove sulfur dioxide from power-plant emissions have helped to keep Ohio coal a marketable commodity. About 25,000 tons are produced annually.

Oil and Gas

Although Ohio is not a major producer of petroleum (oil) and natural gas on a global or national scale, the state has long had important production of these commodities. Soon after Col. Edwin L. Drake’s famous first oil well in 1859 in Titusville, Pennsylvania, drilling began in adjacent areas in Trumbull County in northeastern Ohio and in Washington County in southeastern Ohio. Although Drake’s well is recognized as the first well drilled specifically for oil, a well drilled for salt brine in 1816 in Noble County, Ohio, struck oil, which was sold as a topical medicine for humans and animals, as a lubricant, and as lamp fuel.

In 1884, natural gas and oil were discovered in northwestern Ohio and an oil boom began. Soon, the area was overrun with drillers seeking oil and wooden derricks dotted the landscape, some almost on top of one another. Several major oil companies got their start in this oil field, which is commonly regarded as the first giant field in the United States. Abundant natural gas associated with the oil was vented and set on fire. This wasteful practice soon resulted in the exhaustion of natural gas from the field and the depressurization of the reservoir so that much, perhaps the majority, of the oil remains in the ground. The oil was derived from the Trenton Limestone of Ordovician age and is sometimes referred to as the Trenton Field.

Edward Orton, professor of geology at Ohio State University and State Geologist of Ohio, devoted much study to the occurrence of oil and gas in the Trenton Field and published extensive reports on the topic. Many drillers and investors thought that these hydrocarbons were being created anew in the rocks below and that the supply would be inexhaustible. Orton pointed out that the deposits were finite and accumulated only under certain conditions. Communities such as Findlay offered free gas to any industry that would relocate to the community and many glass plants and other energy dependent industries took advantage of the offer. However, the wasteful practice of venting gas to the atmosphere soon resulted in a natural-gas shortage in the area, just as Orton had predicted.

Since the beginning of production in Ohio, at least 1.1 billion barrels of oil and 8 billion MCF (thousand cubic feet) of natural gas have been produced. Drilling activity and production vary depending on the price of oil and gas, but recent data indicate more than 700 wells drilled annually in 47 counties, mostly in eastern Ohio. More than 300 of these wells were drilled to the Silurian “Clinton-Medina” unit. Annual value of oil was nearly $300 million and $760 million for natural gas.

Petroleum and natural gas are the chemically altered remains of microscopic plants and animals that lived in abundance in ancient seas. As these remains settled with sediment to the bottom of oxygen-poor seas and were buried beneath thick layers of sediment, hydrocarbons (hydrogen and carbon) were altered to waxy kerogen in black shale such as the Ohio Shale. As the rock became more deeply buried and warmer, oil began to form from the kerogen at about 90 degrees C and then to natural gas at about 160 degrees C. Temperatures above 250 degrees C destroyed the oil and gas. This temperature range is known as the Oil Window. Later, the oil and gas may flow from the source rock to a reservoir rock where it may be trapped between the sediment grains and discovered and produced by oil and gas companies.

Industrial Minerals

Limestone and Dolomite

Ohio has an abundance of limestone and dolomite (collectively referred to as carbonate rocks) and has long been an important producer of these sedimentary rocks. Both rock types have a high percentage of calcium carbonate (the mineral calcite) but dolomite has a significant percentage of magnesium. These rocks formed as limy mud in shallow tropical seas that blanketed Ohio periodically during the Paleozoic Era. Most production of these commodities comes from rocks of Silurian and Devonian age in the western half of the state but limestone is produced from Mississippian and Pennsylvanian-age rocks in eastern Ohio.

Traditionally, Ohio ranks fourth in the nation in production of carbonate rocks and limestone and dolomite account for more than half of the annual value of industrial minerals produced in the state. They are quarried in 48 counties, annually producing 79 million tons valued at $471 million. Most of the limestone and dolomite produced in Ohio is used for construction aggregate for roads and building projects and an aggregate in concrete and asphalt. However, these commodities are an important source of agricultural lime, a fluxing agent used in making steel, cement, building stone, and many uses in the chemical industry.

Sand and Gravel

Sand and gravel deposits are abundant in Ohio and are primarily a result of deposits formed by running water during the Pleistocene Ice Age. The terms sand and gravel refer to size of the grains of the materials rather than their composition. The generally rounded grains are rock fragments of sedimentary, metamorphic, and igneous rocks. The latter two categories represent rocks transported by glaciers from Canada and deposited in Ohio as the ice melted. Large volumes of melt water from the glaciers filled river valleys with sand and gravel in deposits known collectively as out wash. Some sand and gravel deposits formed in sub-glacial tunnels (eskers) or in holes in the ice or along the ice edge as conical hills (kames). These loose, unconsolidated materials are easily mined in open-pit surface mines.

Ohio ranks sixth nationally in sand and gravel production and produces 52 million tons annually, valued at $247 million. These deposits are mined in 64 Ohio counties, including deposits dredged from the bed of Lake Erie. Ohio is fortunate to have such widespread abundance of these commodities as transportation costs are greatly reduced if the deposits are close to their point of use. Most sand and gravel is used for construction in road-base material, as an aggregate in concrete and asphalt, glass making, and molding sand for casting iron and aluminum. Sand and gravel deposits are important aquifers for ground water.

Sandstone and Conglomerate

Sandstone and conglomerate are fine-to-medium or coarse-grained rocks, respectively, that represent sand and gravel deposits in which the individual grains are held together by mineral cement. Most sandstone and conglomerate deposits are in the eastern half of the state in rocks of Devonian (Berea Sandstone), Mississippian (Black Hand Sandstone, Buena Vista Sandstone), and Pennsylvanian (Sharon sandstone and conglomerate, Massillon Sandstone) age. These deposits were formed as beaches and bars or in stream channels.

Ohio ranks third in production of dimension sandstone, which is cut into blocks and used in buildings and for decorative stone. These commodities are mined in 18 Ohio counties and have annual production valued at $44 million. In addition to dimension stone, Ohio sandstone is used for many glass products, filtration sand, grindstones, rip-rap, and many other industrial uses. Many historic buildings in Ohio and adjacent areas are constructed from Ohio sandstone.

Clay and Shale

Clay is composed of very fine-grained clay minerals, is not layered and has a plastic consistency. Clay deposits in Ohio were formed as ancient soils beneath coal beds (underclays) of Pennsylvanian age or deposited in glacial lakes during the Pleistocene Ice Age. Shale is a fine-grained rock composed of clay minerals but differs from clay primarily because it is bedded (layered).

Ohio ranks fifth in production of clay and shale with a total value of about $11.9 million from 2.24 million tons of annual production. Clay is produced in 19 counties and shale in 18 counties. Pennsylvanian-age underclays are present in the eastern half of the state whereas production from Pleistocene deposits is from the western part of the state.

Ohio has long been a center of the clay and shale industry. During the 1900s and early 1900s, many companies produced brick, common clay products such as sewer tile, and decorative ceramic pottery. Although many of these companies have ceased operation, Ohio clays and shale are still used to produce brick, tiles, ceramics, as a component of cement, and in the manufacture of paper, cosmetics, and many other products. Much of the clay mined is used as liners for landfills and ponds.


Salt, the mineral halite (sodium chloride), was Ohio’s first commercially exploited mineral resource when salt springs were placed under control of the state soon after Ohio entered the Union. Salt was produced at these operations by evaporating salty water (brine) that naturally came to the surface and evaporated so the salt could be obtained. Late in the 1800s, rock salt was discovered in the Cleveland area during drilling of an oil well. For many years (and continuing today), salt was obtained from these thick, subsurface beds by pumping hot water into wells drilled into the salt and pumping out the salty water that could then be evaporated to obtain the salt. In the late 1950s, underground mines were developed on the Lake Erie shore to exploit the thick salt beds lying about 2,000 feet beneath Lake Erie. These mines, at Cleveland and Fairport Harbor, are still in operation and produce most of the salt in Ohio. Nationally, Ohio ranks fourth in salt production.

Ohio’s rock salt deposits are of Silurian age and formed in a shallow sea that covered Ohio and adjacent areas. It is thought that a series of reefs fringing Ohio restricted circulation of waters from the open sea causing the sea water to evaporate and become so concentrated in salt that this mineral precipitated onto the ocean floor. Thick salt beds now underlie the eastern half of the state. It has been estimated that Ohio’s reserves of salt could supply the entire nation’s needs for 32,000 years.

Ohio production of rock salt was just over 5 million tons valued at $124 million. Most production was from the two underground mines, one each in Cuyahoga and Lake Counties, and three brining operations in Licking, Summit, and Wayne Counties. The brining operations in Summit and Wayne Counties produced artificial brine from Silurian rock salt and the operation in Licking County produced salt from natural brine.

Most rock salt mined in Ohio is used for snow and ice control on roads. Smaller amounts are used as an additive to food products, as a water-softening agent, and other commercial uses.

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