Sand and gravel
Clay and shale
Industrial and metallic minerals research
Kentucky Transportation Cabinet Aggregate Source Book
Technical
Industrial minerals, as used here, are non-fossil fuel rocks, minerals, and sediments that have an industrial use. We subdivide them into two broad groups, bulk rocks, and ore minerals. Bulk rocks are those that are used as aggregate, or for the production of lime, ceramics, Portland cement, or as a product used in coal-fired electricity-generating plants for the removal of sulfur. These bulk rocks or sediments include limestone, dolostone, clay, shale, sandstone, sand, and gravel. The ore minerals are mineral concentrations found in veins or in uncommon sedimentary rocks. Ore minerals that have been produced in Kentucky include calcite, barite, gypsum, fluorspar (fluorite), sphalerite, galena, saltpeter, and various phosphate and iron minerals. Other mineral occurrences, such as titanium-rich sands, may have commercial potential.
Rock: Any naturally formed material composed of one or more minerals having some degree of chemical and mineralogic constancy.
Mineral: A naturally formed chemical element or compound having a definite chemical composition and, usually, a characteristic crystal form.
Sediment: Solid fragmental material, or a mass of such material, that originates from weathering of rocks and is transported by, suspended in, or deposited by air, water, or ice, or that is accumulated by other natural agents, such as chemical precipitation from solution or secretion by organisms, and that forms in layers on the Earth's (or other planet's) surface in a loose, unconsolidated form; e.g., sand, gravel, silt, mud.
Limestone: A sedimentary rock consisting chiefly of the chemical calcium carbonate, primarily in the form of the mineral calcite (more rarely, aragonite).
Dolostone: A carbonate sedimentary rock consisting chiefly of the chemical calcium-magnesium carbonate, primarily in the form of the mineral dolomite, or approximating the mineral dolomite in composition, or a variety of limestone or marble rich in magnesium carbonate.
Clay: (a) A rock or mineral fragment or a detrital particle of any composition (often a crystalline fragment of a clay mineral), smaller than a very fine silt grain, having a diameter less than 1/256 mm. (b) A loose, earthy, extremely fine-grained, natural sediment or soft rock composed primarily of clay-size or colloidal particles and containing a considerable amount of clay minerals (hydrous aluminum silicates).
Shale: A fine-grained, indurated, sedimentary rock formed by the consolidation of clay, silt, or mud, and characterized by very thin layers, and by a composition with an appreciable content of clay minerals, and commonly with a high content of quartz sediment.
Sandstone: A medium-grained sedimentary rock composed of abundant fragments of sand size, more or less firmly united by a cementing agent; the consolidated equivalent of sand, intermediate in texture between conglomerate and shale.
Sand: (a) A rock fragment or particle smaller than a granule and larger than a coarse silt grain, having a diameter in the range of 1/16 to 2 mm. (b) A loose aggregate of unconsolidated mineral or rock particles of sand size.
Gravel: An unconsolidated, natural accumulation of rock fragments resulting from erosion, consisting predominantly of particles larger than sand (diameter greater than 2 mm), such as boulders, cobbles, pebbles, granules, or any combination of these.
Calcite: The most common crystalline or mineral form of calcium carbonate; a common rock-forming mineral.
Barite: The crystalline or mineral form of barium sulfate.
Gypsum: A widely, distributed mineral consisting of hydrous calcium sulfate; it is the most common sulfate mineral.
Fluorspar (fluorite): The crystalline or mineral form of calcium fluoride.
Sphalerite: A crystalline or mineral form of zinc-iron sulfide.
Galena: A crystalline or mineral form of lead sulfide.
Saltpeter: Naturally occurring potassium nitrate.
Kentucky has numerous industrial mineral resources, including limestone, clay, sand, and gravel. Limestones are marine carbonate rocks that range from being very fine grained to very coarse grained and fossiliferous. The chemical quality of a carbonate rock (high calcium or low silica) is important for particular uses. Dolostone and sandstone have also been produced for aggregate materials. Clays are divided into common clays, flint clay, and ball clays. Kaolinite is the principal mineral in most commercial clays. Bentonite and montmorillonite are special clays that expand when wet. The sand and gravel category is a mixture of various sizes of sands, pebbles, gravels, and sometimes boulders. Some of the sand and gravel deposits in northern Kentucky were deposited by glacial meltwater streams. High-purity silica sands also occur in eastern and western Kentucky. Other mineral resources found in Kentucky include iron, titanium, phosphates, and vein minerals such as fluorite, barite, galena, sphalerite, and calcite.
Limestone covers 25 percent of Kentucky's land surface in central, south-central, and southwestern Kentucky. Sand and gravel occurs near the Ohio and Kentucky Rivers and other major stream beds. Clays are found in the Jackson Purchase Region and also in eastern Kentucky near Rowan and Bell Counties. Iron and phosphates occur in eastern and central Kentucky, titanium occurs in the Jackson Purchase Region, and vein minerals occur in central and western Kentucky.
Limestone: Limestone is used as construction aggregate, for building stones, and for agricultural uses. Limestones of high chemical quality are used as sulfur sorbents to control acid mine drainage. Limestones with low silica content are used as rock dust in underground coal mines. Lime, which is a derivative product of limestone, is used as a sulfur sorbent in utility and power plant flue-gas desulfurization.
Clay: The chemical quality of a particular clay determines its use. Clays are used in the manufacture of bricks, tile, chinaware, kitty litter, and other absorptive products, and as fillers and extenders. Kentucky has several plants that produce brick and clay tiles. Bentonitic clays are used as oil drilling fluids or in other products in which their expansive properties are desired for water sealing or retention.
Sand and gravel: Sand and gravel are used as construction aggregates, and silica sands are used in various glasswares.
Others: Iron and titanium are used in steel, and phosphates for fertilizer. Fluorite is the source of fluorine, which is used mainly as flux in the making of steel and for the preparation of hydrofluoric acid. Barite is used as a drilling fluid in oil fields, galena is a source of lead, and the zinc in sphalerite is used as a galvanizing agent.
Kentucky has over 100 mines and quarries from which limestone, clay, and sand and gravel are extracted. One of the largest limestone quarries in the United States is located in western Kentucky. A large limestone mine is located under parts of Lexington. Several clay mines are in the Jackson Purchase Region, and numerous sand and gravel operations (including river dredges) are along the Ohio River. Limestone, clay, and sand and gravel mines are usually surface operations, but many limestone mines are operated underground. During the early 1900's Kentucky was a major center for mining iron, phosphates, barite, galena, and sphalerite, but the discovery of larger deposits elsewhere made these deposits uneconomic.
In 1992, 58 million tons of limestone valued at over $251 million were produced from 86 quarries. Sand and gravel valued at over $34 million, totaling 9.5 million tons, were produced from 20 pits and dredges. Clays valued at $2,942,000, totaling 707,587 tons, were produced from 18 pits.
The Kentucky Geological Survey conducts research, provides public service assistance, and has publications and other information on each of these mineral commodities. For more information, contact Warren Anderson, Kentucky Geological Survey, 228 Mining and Mineral Resources Building, University of Kentucky, Lexington, KY 40506-0107, (606) 257-5500.
Information may also be available from the following organizations:
Kentucky Department of Mines and Minerals (606-254-0367)
Kentucky Sand and Gravel Association (502-584-0158)
Kentucky Crushed Stone Association (502-223-2379)
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