Minerals and mineral products of Texas are presented alphabetically in this article.
Aluminum. Three Texas plants produce aluminum oxide from imported aluminum ore (bauxite). Aluminum processing plants are located in Calhoun, Milam, and San Patricio counties.
Antimony. Although antimony ore is not produced in Texas, antimony ores are processed at a smelter in El Paso.
Asbestos. Amphibole asbestos is associated with talc deposits in Hudspeth County. Tremolite asbestos occurs in some of the Precambrian metamorphic rocks of the Llano region. No asbestos is mined in Texas.
Asphalt. Numerous deposits of asphalt-bearing rocks occur in Texas. They include asphaltic Cretaceous limestones in Bexar, Burnet, Kinney, Uvalde, and other counties. Large amounts of the asphaltic limestone are quarried in Uvalde County for use chiefly as paving material. Asphaltic Cretaceous sandstones, which are not currently quarried, occur in Cooke, Montague, Uvalde, and other counties.
Barite. Deposits of barite are widely distributed in Texas, but most are minor. They occur in Baylor, Brewster, Culberson, Gillespie, Hudspeth, Jeff Davis, Llano, Taylor, and other counties. During the 1960s barite was mined in the Seven Hart Gap area for use as a weighting agent in rotary-drilling muds.
Basalt. Intrusive masses of basalt are present in several counties along the Balcones Fault Zone and in the Trans-Pecos area of West Texas. It is produced for aggregate, road ballast, and road material in Uvalde County.
Beryllium. Beryllium minerals are present at several localities in the Trans-Pecos area of West Texas. In recent years a beryllium prospect has been located in Hudspeth County near Sierra Blanca where several beryllium minerals are associated with fluorspar, but no production has been reported.
Bismuth. Bismuth occurs in association with molybdenum and gold in a Precambrian pegmatite dike at the Kiam prospect on Honey Creek in Llano County. It was found also in small quantities in the old Heath gold prospect in Llano County. No bismuth has been produced commercially in Texas.
Bleaching clay. Bentonite clays that are commonly used as bleaching clays and fuller's earth occur at numerous localities in Tertiary formations of the Coastal Plain and deposits on the High Plains. Bleaching clays are used for refining petroleum products and to a lesser extent for refining vegetable oils. Texas bleaching clays are currently produced in Fayette and Gonzales counties.
Brines. Brines containing strong concentrations of mineral salts occur in a variety of geological conditions in widely separated areas of Texas. Shallow brines occur in broad shallow basins usually occupied in part by one or more saline playas or alkaline lakes. Surface and seep waters draining into the playas undergo rapid natural evaporation, resulting in the concentration of salts leached from soils and rocks of the drainage area. Shallow brines are produced for sodium sulfate in Gaines and Terry counties. Brine reservoirs containing salts of sodium, calcium, magnesium, potassium, and other elements are present in the Permian Basin. These aquifers lie at considerable depth and have not been produced commercially for their salts. In Trans-Pecos Texas shallow brines containing mainly common salt and gypsum occur in the Salt Basin in northern Culberson and Hudspeth counties. Highly gypsiferous waters are present in eastern Culberson County and parts of Reeves County. In southern Texas, brines containing sodium chloride and other salts occur in La Sal del Rey and La Sal Vieja in Willacy and Hidalgo counties. No salts are produced from these brines. Local brine areas are known in the vicinity of salt domes in the Texas Coastal Plain. In parts of East Texas, some moderately strong brines occur in saliferous Tertiary formations not related to salt domes.
Bromine. Bromine is extracted from seawater at Freeport in Brazoria County.
Caliche. Caliche occurs abundantly in surface and near-surface deposits in the semiarid and arid parts of Texas and is particularly abundant in the High Plains and the outcrop belt of the Goliad Formation of South Texas. A large quantity of caliche is produced chiefly for road construction from numerous and widespread localities.
Celestite. Celestite is known at numerous localities, particularly in the Cretaceous Glen Rose Formation and the Upper Permian Whitehorse Formation in North and north central Texas, respectively. These occurrences are small and have no commercial value. Extensive deposits of celestite are present in Brown and Nolan counties. Small quantities of celestite were produced from these counties during the late 1930s and early 1940s. Most of the celestite produced in Texas has been used as a weighting agent in rotary-drilling fluids.
Cement. Limestone and clay are the principal components used in the manufacture of cement. Iron ore and gypsum are also used in smaller amounts. Cement is currently produced in Bexar, Comal, Dallas, Ector, Ellis, El Paso, Harris, Hays, McLennan, Nolan, Nueces, Potter, and Tarrant counties. Portland cement output rose slightly during 1989 to a total of 7.2 million short tons with a value of $286 million. Historically, the state's portland cement output has accounted for about 10 percent of the annual United States production. Texas usually has been ranked first or second among the thirty-eight producing states. In 1989 Texas was ranked second behind California. Masonry cement continued its five-year downtrend, and output was estimated at less than half of that in 1984. Declines in Texas construction industries generally have caused a decrease in demand for portland cement. Texas Portland cement production was up 200,000 tons over that of 1988 but was still lower than the 1975 production. The demand for masonry cement has fallen every year since a record high of 291,000 short tons in 1984.
Clay. Texas has an abundance of various types of clays, occurring in many geologic units. Production includes ball clay, bentonite, common clay and shale, fire clay, fuller's earth, and kaolin. Texas is one of the leading producers of clays in the United States. Ceramic products include structural building brick, paving brick, decorative tile, drain tile, and expanded clay for lightweight aggregate. Common clay suitable for the manufacture of cement or common brick is found in many counties. Clays suitable for ceramic and refractory ware contain a high proportion of kaolin and are found primarily in northeastern Texas. Nonceramic clays are used as bleaching or adsorbent clays, fillers, coaters, additives, bonding clays, drilling muds, and catalysts. Most nonceramic products are produced from bentonites that are found primarily in the Coastal Plain. Kaolin clays found in East Texas are used as paper coaters and fillers and rubber fillers. High-purity kaolin clays have a high alumina content and are a potential source of metallic aluminum.
Coal. Bituminous coal of Pennsylvanian age occurs primarily in Coleman, Eastland, Erath, Jack, McCulloch, Montague, Palo Pinto, Parker, Throckmorton, Wise, and Young counties of north central Texas. Bituminous coal deposits are also found in Cretaceous deposits of the Olmos Formation in Maverick County and in Eocene age cannel coal deposits in Webb County. These coals provided a significant energy source prior to the development of oil and gas in the 1940s. Mines in these areas were inactive from the early 1940s until the 1970s, when high petroleum prices prompted a revaluation of the Texas coal deposits. Limited bituminous coal production in these areas was resumed during the late 1970s. A decline in demand during the late 1980s resulted in the closing of the North Texas coal mines. The mines in Webb County reduced production but were still in operation in 1992. Cretaceous bituminous coals in Trans-Pecos Texas have little potential for development as a fuel. They have been marketed primarily as a soil conditioner (leonardite). Commercial mining for coal and lignite started in the late 1880s. The first year coal production was listed for Texas was 1884, when 125,000 short tons was mined. Production declined from 1885 to 1888. It subsequently climbed at a high rate to 1,107,953 short tons in 1901, then gradually increased to a high of about 2.4 million tons in 1913. After that year, coal and lignite production gradually declined. Annual production fell below one million short tons in 1930 and below 100,000 short tons in 1945. Production of bituminous coal ceased in 1944; production of lignite continued but declined drastically during the early 1950s. Coal and lignite were mined primarily by underground methods until the 1950s. In the mid-1950s the industry received a tremendous boost when Aluminum Company of America started using char produced from lignite at its plant near Rockdale. In 1954 estimated lignite production exceeded a million short tons. The production of lignite by strip-mining methods and the utilization of lignite to fuel mine-mouth generators for the production of electricity caused Texas to become a major coal (lignite) producer during the 1970s. Coal production in Texas now exceeds fifty million short tons annually.
Copper. Copper deposits in Texas occur in the Trans-Pecos region, in the Permian red beds of north central Texas, and in the Llano region. Mining has been attempted at different times on the deposits in each region. Most of the state's small production has been from the Van Horn-Allamoore mining district, whereas only small shipments of copper have been reported from the North Texas and Llano regions. The last reported copper production was eighteen tons in 1952, valued at $8,712. Most of the ore came from the Old Hazel Mine in Culberson County. During the mid 1950s, however, most of the Texas copper mines were inoperative. Large deposits of ore exist in North Texas but have not been developed because of their low metal content. Copper refineries operate in El Paso and Potter counties. Copper smelters are operating in plants at Amarillo, El Paso, and Texas City. These depend upon imported ore from Arizona, Chile, New Mexico, and Mexico to produce refined copper, copper anode, copper sulfate, and other copper products.
Diatomite. Diatomite, or diatomaceous earth, occurs in the upper Tertiary and Pleistocene lacustrine deposits on the High Plains. No Texas diatomite has been produced.
Dolomite. Dolomite is widely distributed in Texas except in the Coastal Plain and over the greater part of the High Plains. It occurs in beds of varying thickness and extent in rocks ranging from Precambrian to Cretaceous in age. Dolomite was mined from the Ellenburger Formation in Burnet County as an ore of magnesium during the 1940s. It was processed in the Austin plant of International Minerals and Chemical Company and the Mathieson Alkali Works, Lake Charles, Louisiana. The Ellenburger dolomites are now used by Dow Chemical at Freeport in Brazoria County as a part of a process of removing magnesium from sea water. Dolomites from the Edwards Formation are used as a source of crushed stone.
Evaporites. Evaporites, including rock salt, gypsum, potassium minerals, and other similar compounds, occur extensively in Permian deposits that underlie the greater part of the High Plains and parts of adjacent regions. The evaporite compounds of West Texas are not being produced, although potash is mined extensively in the vicinity of Carlsbad, New Mexico. Salt, anhydrite, and gypsum occur in the salt domes of the Coastal Plain. These minerals, except anhydrite, are considered separately.
Feldspar. Feldspar occurs in Precambrian formations in parts of the Llano and Trans-Pecos regions. During the 1950s it was produced from pegmatite dikes in Llano and Culberson counties and used in the manufacture of pottery, ceramics, and glassware. Feldspars are not currently being produced in Texas.
Fluorspar. Fluorspar or fluorite is an important industrial mineral used in the manufacture of steel, aluminum, glass, and fluorocarbons. It occurs at several localities in the Trans-Pecos and Llano regions of Texas. Trans-Pecos deposits are commonly associated with Tertiary volcanics and Cretaceous limestones. Mining operations first started in 1943 at Eagle Mountain in Hudspeth County. Occurrences of fluorspar have also been found in the Quitman Mountains of Hudspeth County, the Chinati Mountains of Presidio County, the Franklin Mountains of El Paso County, and the Christmas Mountains and other areas of Brewster County. The fluorspar in the Llano region occurs in pegmatite dikes and lenses and veins in Precambrian schists and gneisses. None of the deposits in Texas are currently being produced.
Gemstones. Collecting gem rock and mineral specimens has attracted numerous fans ("rockhounds") and has proved quite profitable. Agate, jasper, cinnabar, fluorite, topaz, calcite, opal, petrified wood, and tektites are stones that are commonly collected by lapidarists. No records are available on the quantities of gemstones collected and sold each year.
Gold. Gold mining has not been extensive in Texas since the occurrence of the metal is limited. Main production, confined to the Presidio and Hazel mines in West Texas and the Heath mine in the Llano region, amounted to a total of 8,277 fine ounces by 1942, valued at $233,499. Most of the gold produced has come as the by-product of silver and copper ores, but traces of it occur in the Shafter, Van Horn, Allamore, and Ouitman Mountains, and in Howard, Taylor, Irion, Uvalde, and Williamson counties with other rocks and ores. The last reported gold production was from the Presidio mine in 1942.
Graphite. Deposits of fine-flake graphite occur in the Precambrian Packsaddle Schist in the Llano region. Graphite was previously produced in Burnet County.
Greensand. Greensand or glauconite sand occurs in Upper Cambrian rocks in the Llano region and in the Midway, Weches, and other Eocene formations in the Texas coastal plain. Greensand has been used in the past as a soil conditioner and in purifying water. It is not currently produced commercially in Texas.
Grinding pebbles. Pebbles suitable for use in grinding mills occur in widely distributed surface deposits along the interior margin of the southern and southwestern Coastal Plain. They have been produced in Bastrop, Colorado, Fayette, Frio, and Gonzales counties. However, modern grinding methods have eliminated the demand for grinding pebbles, and there is no current production of these materiels.
Guano. Bat guano occurs in numerous caverns in the Edwards Plateau and in the Trans-Pecos region and to a more limited extent in Central Texas. Guano has been produced in Edwards, Medina, Real, and other counties. No current production is known in Texas.
Gypsum. Gypsum is widely distributed and extensively developed in Texas. The main occurrences are (1) in the Blaine and other Permian formations that crop out east of the High Plains; current mining from these extensive bedded deposits occurs in Fisher, Hardeman, and Nolan counties; (2) in the Permian Castile gypsum that crops out in large areas between the Delaware and Apache Mountains and Pecos River in Culberson and Reeves counties; (3) in rocks of probable Permian age in the vicinity of the Malone Mountains in Hudspeth County; (4) in the Cretaceous Edwards Formation in Gillespie and Menard counties, mined in Gillespie County; (5) in caprocks of the Gulf Coast salt domes mined at Hockley dome in Harris County and previously at Gyp Hill in Brooks County. Gypsum is used in the manufacture of plaster of paris, wallboard, and cement.
Helium. Texas is the leading producer of helium, which is extracted from natural gas in the Panhandle area at a United States Bureau of Mines plant in Moore County and at two privately owned plants in Moore and Hansford counties. Production is from the Cliffside gas field near Amarillo.
Iron. Deposits of iron ore, including siderite and the limonite-group minerals, are present in the Eocene Weches Formation in northeastern Texas. Deposits are present in Anderson, Camp, Cass, Cherokee, Harrison, Henderson, Marion, Morris, Nacogdoches, Smith, and Upshur counties. Deposits in Cherokee and Henderson counties are mined chiefly as a source of iron for the manufacture of cement. Several deposits of iron ore minerals are present in Central Texas, such as the magnetite deposits at Iron Mountain in Llano County and the hematitic sandstone deposits in Llano, Mason, McCulloch, and San Saba counties. Hematite also is present in the Trans-Pecos.
Lead and Zinc. Lead and zinc are commonly considered together because they are generally associated in mineral deposits. These metals occur in small deposits in Texas, and much of their past production has been as a by-product in the production of silver. A large part of the lead was obtained as a minor product of silver-lead ores taken from the Presidio mine in Presidio County. Practically all of the state's zinc production and an approximately equivalent amount of lead was produced from the Bonanza and Alice Ray mines in Hudspeth County from ores with a small silver content. Lead and zinc are also present in the Quitman Mountains southwest of Sierra Blanca in Hudspeth County and in the Apache Mountains in Culberson County. Lead deposits are known at several localities in Cambrian strata in Blanco, Burnet, and Gillespie counties in Central Texas. The only reported production from the Central Texas area was in 1930 from the Pavitte prospect in western Burnet County. Lead and zinc are not currently produced in Texas and have not been mined in the state since 1952. Between 1885 and 1952 the total lead production in Texas amounted to 5,443 short tons and the total zinc production was 837 short tons. Lead was formerly produced as a by-product of silver mining, mainly from the Presidio Mine in Presidio County and the Bird Mine in Brewster County. Zinc production had come chiefly from the Bonanza and Alice Ray mines in Hudspeth County, with small amounts also from the Chinati and Montezuma mines in Presidio County and the Buck Prospect in Culberson County. Although no longer a producer of lead and zinc, Texas had a primary smelter that produced lead and zinc in El Paso County until the mid-1980s. The ore came from western states and Mexico.
Lignite. Lignite or brown coal occurs in extensive deposits in the Eocene, Wilcox, and Claiborne groups of the Texas Coastal Plain. The Wilcox Group contains the largest reserves and highest quality lignite. The principal resource area is north of the Colorado River in Central and East Texas. Lignite was first mined in Texas during the 1850s and was produced primarily from underground mines. Lignite production declined during the 1940s and early 1950s, when oil and gas supplies became readily available. Recovery of the Texas coal-mining industry began in the 1950s, when strip-mining techniques were first used to mine Texas lignite and provide a feed stock to mine-mouth electrical generators. Texas is now the nation's sixth-largest coal producer, with estimated recoverable near-surface reserves (at depths of less than 200 feet and seam thicknesses of three or more feet) of twenty-three billion short tons. Lignite is currently utilized at electrical generators in Atascosa, Bastrop, Freestone, Grimes, Harrison, Hopkins, Limestone, Panola, Rusk, and Titus counties. It is also produced in Harrison County as a source of activated carbon. Deep-basin lignite resources (200 to 2,000 feet deep) are approximately equal to near-surface lignite resources. These resources can be developed by the process of in situ gasification.
Lime. Limestones, which are abundant in many parts of Texas, are utilized in the manufacture of lime. They are crushed and calcined to drive off the excess carbon dioxide and convert the calcium carbonate to calcium oxide (see LIMEKILNS). Uses of lime include soil stabilization, water purification, paper and pulp manufacture, metallurgy, sugar refining, agriculture, construction, and removal of sulfur from power plant stack gases. Plants for the production of lime are currently operating in Bexar, Bosque, Burnet, Comal, Deaf Smith, Hill, Johnson, Nueces, and Travis counties.
Magnesite. Magnesite occurs in Precambrian deposits commonly associated with marbles. Small-scale mining operations in Llano and Mason counties have extracted magnesite for use as agricultural stone and terrazzo chips.
Magnesium. Magnesium chloride, magnesium sulfate, and other mineral salts are present in Upper Permian brines in Borden County and in shallow brines underlying playas in the High Plains. Magnesium chloride is extracted from sea water at a plant in Brazoria County and is used to produce magnesium compounds and magnesium metal.
Manganese. Manganese is known to occur in residual and surficial deposits in Precambrian rocks in Mason and Llano counties, at several localities in Cretaceous and Quaternary deposits in Val Verde County, in Lower Cretaceous deposits in Jeff Davis County, and in Triassic sandstones in Dickens County. Small quantities of manganese have been mined from the deposits in Jeff Davis County, but no production has been reported since the mid-1950s.
Mercury. Mercury mineral deposits occur in the Terlingua district of southern Brewster and southeastern Presidio counties, where mining was initiated in 1896. During the early 1930s Texas was one of the nation's leading producers of mercury. The sharp reduction in price and demand after World War II caused the closure of all Texas mercury mines. A rise in price during the 1950s caused sporadic mining activity in the area. Record high prices for mercury in the middle to late 1960s prompted renewed interest in the area that resulted in the reopening of several mines and the discovery of new reserves. All of the mines closed in the early 1970s, when prices again declined. No production has been reported since 1973.
Mica. Mica is present in Precambrian pegmatite dikes on the western side of the Van Horn Mountains in western Culberson County and also in Precambrian schists and pegmatites in the Llano region. Some mica has been produced in the past from the Culberson County area, but production is no longer active.
Mineral water. Water containing high concentrations of salts and bitterns has been extracted from a variety of groundwater horizons. Mineral water has been produced at Mineral Wells in Palo Pinto County, near Marlin in Falls County, at Milford in Ellis County, and at Thorndale in Williamson County. No production of mineral waters is currently reported.
Molybdenum. Deposits of molybdenum minerals have been found in Brewster, Culberson, Hudspeth, Llano, and Presidio counties, but no production has been reported.
Nitrates. Sodium nitrate and potassium nitrate are present in volcanic rocks in the vicinity of Candelaria, but attempts at production have been unsuccessful.
Novaculite. Novaculite, a chert-like, siliceous rock, occurs in the Caballos Formation of Devonian age that crops out in prominent ridges in the Marathon area in Brewster County. It is not produced in Texas.
Opal. Common opal associated with chalcedony occurs in the Catahoula and other Tertiary formations of the Texas Coastal Plain. Opal also occurs as nodules and masses, as cement in sandstones, as vein and cavity fillings, and as a replacement of wood.
Oyster shell. Oyster and clam shells occur in reefs and beds in the bays and lagoons bordering the Gulf of Mexico and in some Quaternary sediments along the seaward margin of the Texas Coastal Plain. Shells from many of these areas were extensively produced until the early 1960s, when production was discontinued because of environmental concerns.
Peat. Peat bogs are widely distributed in the middle and eastern part of the Coastal Plain at localities in Gonzales, Guadalupe, Lee, Milam, Polk, and San Jacinto counties. Peat from some of these deposits has been produced in the past for use as a soil conditioner.
Perlite. Perlite is a glassy igneous rock that expands to a porous lightweight mass when heated. Its uses include filter medium, lightweight aggregate, and horticultural aggregate. Perlite has been produced near Pinto Canyon in Presidio County. No perlite is currently produced in Texas, but imported perlite is processed at plants in Bexar, Dallas, El Paso, Guadalupe, Harris, and Nolan counties.
Phosphate. Small quantities of phosphate rock are present in Paleozoic formations in West and Central Texas. Upper Cretaceous and Tertiary deposits in northeastern Texas also contain lenses of rock phosphate. No phosphate is mined in Texas, but imported phosphate rock is processed at a plant in Brownsville.
Potash. Potash minerals, including polyhalite, are found in extensive deposits in Permian strata in parts of West Texas. After World War I a search for potash sources, conducted by state and federal agencies, resulted in the development of high-grade potash rock containing sylvite and other potash minerals in New Mexico. Texas potash deposits are of a lower grade and have not been developed.
Pumicite. Volcanic ash or pumicite occurs in numerous deposits in some of the Tertiary formations of the Texas Coastal Plain, particularly in the Catahoula and Jackson formations. Other Tertiary ash deposits occur in volcanic rocks in the Trans-Pecos. Pleistocene volcanic-ash deposits occur at several localities in the High Plains and eastward as far as Wichita County. Volcanic ash was formerly mined in Dickens, Gonzales, Lynn, Scurry, and Star counties.
Rare-earth minerals. Elements of the Lanthanide series are commonly termed rare-earth elements. Yttrium is also commonly included in the group because it is associated with the heavier rare earths. Several of the rare earths have anomalous concentrations in the rhyolitic and related igneous rocks in the Quitman Mountains and the Sierra Blanca area of Trans-Pecos Texas. A deposit containing several rare-earth minerals was exposed at Barringer Hill in Llano County before it was covered by the waters of Lake Buchanan. No rare earths are produced in Texas.
Salt. Salt occurs in large quantities in salt domes in the Texas Coastal Plain and with other evaporites in the Permian Basin of West Texas. Smaller quantities are present in surface and near-surface brines and in playas and saline springs in West and South Texas. Rock salt is produced from an underground mine at Grand Saline in Van Zandt County. However, most of the salt production in Texas is from brine wells. Texas is one of the leading salt-producing states.
Sand and gravel. Sand and gravel deposits of commercial value are found adjacent to the major rivers that flow across Texas and in the Goliad, Uvalde, and Willis formations in the Texas Coastal Plain. Extensive deposits also occur in Seymour Formation gravels and basal Cretaceous formations in north central Texas, in alluvial fan deposits east of the Caprock, and in the mountain areas of Trans-Pecos Texas. Sand and gravel deposits are mined primarily as a source of construction materials. The principal sand and gravel producing counties in Texas include Bexar, Brazos, Colorado, Dallas, Ellis, Fayette, Hays, Hidalgo, Johnson, Kaufman, Liberty, McLennan, Montgomery, Parker, Pecos, Reeves, Travis, Val Verde, Victoria, and Wise counties.
Sands. Sands used for industrial purposes commonly have unique physical or chemical characteristics that make them suitable for special purposes. Most of these sands have a high silica content. Sands suitable for industrial use occur in Tertiary deposits of the Texas Coastal Plain and East Texas, Cretaceous formations of north central Texas, and Paleozoic rocks of Central Texas. Industrial sands produced in Texas include abrasive, blast, chemical, engine, filtration, foundry, glass, hydraulic-fracturing, molding, and pottery sands. These are produced from formations in Atascosa, Bowie, Colorado, El Paso, Gonzales, Guadalupe, Hardin, Harris, Johnson, Liberty, Limestone, McCulloch, Newton, Smith, Somervell, Upshur, and Wood counties.
Silver. The discovery of silver in Texas has been credited by some to Franciscans who discovered and operated mines near El Paso about 1680. Reportedly, these mines were worked periodically, closed down and concealed, and later rediscovered. However, no documentation of these operations is available. Documented silver production started in the late 1880s at the Presidio Mine, near Shafter in Presidio County. About 1885 silver mining began in the Van Horn-Allamoore district in Hudspeth and Culberson counties. Other areas where silver has been produced in Texas include the Shafter district, northern Quitman Mountains district, Loma Plata mine, Altuda Mountain district, Eagle Mountains district, and Van Horn Mountains district. Between 1885 and 1955, Texas produced 32,663,405 troy ounces of silver.
Stone, crushed. Texas is among the nation's leading producers of crushed stone. Crushed stone can be produced from many varieties of igneous, metamorphic, and sedimentary rocks. Most crushed stone produced in the state is limestone. Other stones that provide smaller volumes of crushed stone include basalt, dolomite, granite, marble, rhyolite, sandstone, and serpentine. Crushed stone is used primarily as aggregate for use in concrete and road material. Large tonnages are also used in the manufacture of lime and cement. Relatively small tonnages of crushed stone are used for fillers, filter material, riprap, roofing chips, and terrazzo.
Stone, dimension. Materials suitable for dimension stone or building stone can be found in most parts of the state except the High Plains and the Gulf Coastal Plain. Granite, limestone, and sandstone are the only stones currently being produced as dimension stone. Granites are produced from Precambrian granites in Burnet, Gillespie, Llano, and Mason counties. Limestones are produced from rocks of Permian age in Jones and Schackelford counties and rocks of Cretaceous age in Lampasas, Travis, and Williamson counties. Sandstones are produced from Triassic deposits in Ward County.
Sulfur. Sulfur occurs in the caprocks of salt domes in the Gulf Coastal Plain, in Permian-age bedded deposits in Trans-Pecos Texas, and as a constituent of sour gas and petroleum. Mining of native sulfur deposits is accomplished by the Frasch process, which uses superheated water to melt the sulfur so that it can be pumped to the surface. Sulfur is used in petroleum refining and in the preparation of fertilizer and chemicals. Texas is one of the nation's leading producers of sulfur. Native sulfur is produced from one salt dome in Wharton County and from subsurface Permian deposits in Culberson County. Recovered sulfur is extracted from oil and gas at more than sixty plants in about thirty-six Texas counties.
Talc. Talc deposits are present in Precambrian metamorphic rocks in the Allamoore area of Culberson and Hudspeth counties and in Blanco, Gillespie, and Llano counties of the Llano Uplift area. Deposits in the Allamoore are currently being produced. Talc is used as a filler in the manufacture of roofing materials, paper, plastic, and synthetic rubber and in ceramic materials.
Tin. The tin mineral cassiterite is present in the Franklin Mountains north of El Paso, where small quantities of tin ore were produced during the early 1900s. Minor quantities have also been found in the Streeter area of Mason County. The only tin smelter in the United States is located at Texas City. Imported ore concentrates and other tin-bearing materials are processed at this plant. Tin is not currently being mined in Texas.
Titanium. The titanium mineral rutile occurs in association with Tertiary silicified tuffs and kaolin at the Mueller prospect in south central Jeff Davis County. The mineral ilmenite also contains titanium and is present in several counties in Gulf Coastal Plain. No deposits of commercial interest have been discovered.
Topaz. Colorless and light-blue varieties of topaz are found in Precambrian granite in the vicinity of Streeter in Mason County. Topaz is not produced commercially.
Tripoli. Tripoli occurs in several deposits in the Marble Falls limestone in southern Lampasas County. The tripoli, a siliceous incoherent material consisting of particles of sponge spicules, has been produced in small quantities, but there is no current production from the area.
Tufa. Tufa and travertine are freshwater limestone deposits commonly associated with springs and streams in the limestone regions of Texas. Tufa deposits were previously produced in San Saba County, but no current production is known.
Turquoise. Turquoise occurs in the Precambrian Carrizo Mountain schist in the Van Horn area near the Culberson-Hudspeth county line. Material has been produced from this area in the past, but no production is known at present.
Uranium. Uranium was discovered in Texas in the mid-1950s in Karnes County. Deposits were found in Tertiary formations in a mineralized zone that extends from the central Coastal Plain southwestward to the Rio Grande. Uranium mineralization was subsequently discovered in the Trans-Pecos area, the Llano Uplift, and the High Plains. A small amount of uranium was produced from deposits in the High Plains during the 1950s, but most of the Texas production has been from the Coastal Plain. In the past uranium was produced from surface mines in Atascosa, Gonzales, Karnes, and Live Oak counties. These mines are now closed and reclaimed. Current uranium production is by in situ leaching. Demand and production of uranium decreased sharply during the 1980s.
Vermiculite. Vermiculite is a mica-like mineral that expands when heated. It is used as a horticultural medium, lightweight aggregate, and insulating material. Deposits are present in Precambrian metamorphic deposits in the Llano region. Exfoliation plants at Dallas, Houston, and San Antonio currently process vermiculite mined outside of Texas. Vermiculite is not currently produced in Texas.
Zeolites. Zeolite minerals occur in Tertiary volcanic deposits in Trans-Pecos Texas and in the Coastal Plain. They are used in ion-exchange processes, as catalysts, in air and water purification, and other purposes. Deposits in McMullen County are currently being produced.
See also CEMENT PRODUCTION, COAL AND LIGNITE MINING, COPPER PRODUCTION, GOLD MINING, HELIUM PRODUCTION, IRON ORE DEPOSITS, IRON AND STEEL INDUSTRY, LEAD AND ZINC PRODUCTION, MERCURY MINING, MARINE RESOURCES, MINERAL RIGHTS AND ROYALTIES, MINERAL-WATER SPRINGS AND WELLS, OIL AND GAS INDUSTRY, POTTERY, SALT INDUSTRY, SILVER MINING, SULFUR INDUSTRY, TIN SMELTING, and URANIUM MINING.