There are many nonpetroleum, or nonfuel, minerals found in Texas. Some are currently mined, and others may have a potential for future development. Still others are minor occurrences only.
Although they are overshadowed by the petroleum, natural gas, and natural gas liquids that are produced in the state, many of the nonpetroleum minerals are, nonetheless, important to the economy. In 2012, nonfuel minerals were valued at an estimated $3.39 billion, representing 4.43 percent of the total U.S. production and ranking Texas eighth among the states in overall U.S. production. In 2011, nonfuel minerals produced in Texas were valued at an estimated $2.81 billion.
The leading mineral commodities produced in the Texas are portland cement, crushed stone, and contruction sand and gravel. These three, together with salt, industrial sand and gravel, lime, and masonry cement, account for more that 95 percent of the state's nonfuel mineral value.
The Bureau of Economic Geology, which functions as the state geological survey of Texas, supplied the following information about nonpetroleum minerals.
Texas’ nonpetroleum minerals are as follows:
ALUMINUM — No aluminum ores are mined in Texas, but three Texas plants process aluminum materials in one or more ways. Plants in San Patricio and Calhoun counties produce aluminum oxide (alumina) from imported raw ore (bauxite), and a plant in Milam County reduces the oxide to aluminum.
ASBESTOS — Small occurrences of amphibole-type asbestos have been found in the state. In West Texas, richterite, a white, long-fibered amphibole, is associated with some of the talc deposits northwest of Allamoore in Hudspeth County. Another type, tremolite, has been found in the Llano Uplift of Central Texas where it is associated with serpentinite in eastern Gillespie and western Blanco counties. No asbestos is mined in Texas.
ASPHALT (Native) — Asphalt-bearing Cretaceous limestones crop out in Burnet, Kinney, Pecos, Reeves, Uvalde, and other counties. The most significant deposit is in southwestern Uvalde County, where asphalt occurs naturally in pore spaces of the Anacacho Limestone. The material is quarried and used extensively as road-paving material. Asphalt-bearing sandstones occur in Anderson, Angelina, Cooke, Jasper, Maverick, Montague, Nacogdoches, Uvalde, Zavala, and other counties.
BARITE — Deposits of a heavy, nonmetallic mineral, barite (barium sulphate), have been found in many localities, including Baylor, Brown, Brewster, Culberson, Gillespie, Howard, Hudspeth, Jeff Davis, Kinney, Llano, Live Oak, Taylor, Val Verde, and Webb counties. During the 1960s, there was small, intermittent production in the Seven Heart Gap area of the Apache Mountains in Culberson County, where barite was mined from open pits. Most of the deposits are known to be relatively small, but the Webb County deposit has not been evaluated. Grinding plants, which prepare barite mined outside of Texas for use chiefly as a weighting agent in well-drilling muds and as a filler, are located in Brownsville, Corpus Christi, El Paso, Galena Park, Galveston, and Houston.
BASALT (TRAP ROCK) — Masses of basalt — a hard, dark-colored, fine-grained igneous rock — crop out in Kinney, Travis, Uvalde, and several other counties along the Balcones Fault Zone, and also in the Trans-Pecos area of West Texas. Basalt is quarried near Knippa in Uvalde County for use as road-building material, railroad ballast, and other aggregate.
BENTONITE (see CLAYS).
BERYLLIUM — Occurrences of beryllium minerals at several Trans-Pecos localities have been recognized for several years.
BRINE (see also SALT, SODIUM SULPHATE) — Many wells in Texas produce brine by solution mining of subsurface salt deposits, mostly in West Texas counties such as Andrews, Crane, Ector, Loving, Midland, Pecos, Reeves, Ward, and others. These wells in the Permian Basin dissolve salt from the Salado Formation, an enormous salt deposit that extends in the subsurface from north of the Big Bend northward to Kansas, has an east-west width of 150 to 200 miles, and may have several hundred feet of net salt thickness. The majority of the brine is used in the petroleum industry, but it also is used in water softening, the chemical industry, and other uses. Three Gulf Coast counties, Fort Bend, Duval, and Jefferson, have brine stations that produce from salt domes.
BUILDING STONE (DIMENSION STONE) — Granite and limestone currently are quarried for use as dimension stone. The granite quarries are located in Burnet, Gillespie, Llano, and Mason counties; the limestone quarries are in Shackelford and Williamson counties. Past production of limestone for use as dimension stone has been reported in Burnet, Gillespie, Jones, Tarrant, Travis, and several other counties. There also has been production of sandstone in various counties for use as dimension stone.
CEMENT MATERIALS — Cement is currently manufactured in Bexar, Comal, Dallas, Ector, Ellis, Hays, McLennan, Nolan, and Potter counties. Many of these plants utilize Cretaceous limestones and shales or clays as raw materials for the cement. On the Texas High Plains, a cement plant near Amarillo uses impure caliche as the chief raw material. Iron oxide, also a constituent of cement, is available from the iron ore deposits of East Texas and from smelter slag. Gypsum, added to the cement as a retarder, is found chiefly in North Central Texas, Central Texas, and the Trans-Pecos area.
CHROMIUM — Chromite-bearing rock has been found in several small deposits around the margin of the Coal Creek serpentinite mass in northeastern Gillespie County and northwestern Blanco County. Exploration has not revealed significant deposits.
CLAYS — Texas has an abundance and variety of ceramic and non-ceramic clays and is one of the country’s leading producers of clay products.
Almost any kind of clay, ranging from common clay used to make ordinary brick and tile to clays suitable for manufacture of specialty whitewares, can be used for ceramic purposes. Fire clay suitable for use as refractories occurs chiefly in East and North Central Texas; ball clay, a high-quality plastic ceramic clay, is found locally in East Texas.
Ceramic clay suitable for quality structural clay products, such as structural building brick, paving brick, and drain tile, is especially abundant in East and North Central Texas. Common clay suitable for use in the manufacture of cement and ordinary brick is found in most counties of the state. Many of the Texas clays will expand or bloat upon rapid firing and are suitable for the manufacture of lightweight aggregate, which is used mainly in concrete blocks and highway surfacing.
Nonceramic clays are utilized without firing. They are used primarily as bleaching and absorbent clays, fillers, coaters, additives, bonding clays, drilling muds, catalysts, and potentially as sources of alumina. Most of the nonceramic clays in Texas are bentonites and fuller’s earth. These occur extensively in the Coastal Plain and locally in the High Plains and Big Bend areas. Kaolin clays in parts of East Texas are potential sources of such nonceramic products as paper coaters and fillers, rubber fillers, and drilling agents. Relatively high in alumina, these clays also are a potential source of metallic aluminum.
COAL (see also LIGNITE) — Bituminous coal, which occurs in North Central, South, and West Texas, was a significant energy source in Texas prior to the large-scale development of oil and gas. During the period from 1895–1943, Texas mines produced more than 25 million tons of coal. The mines were inactive for many years, but the renewed interest in coal as a major energy source prompted a revaluation of Texas’ coal deposits. In the late 1970s, bituminous coal production resumed in the state on a limited scale when mines were opened in Coleman, Erath, and Webb counties.
Much of the state’s bituminous coal occurs in North Central Texas. Deposits are found there in Pennsylvanian rocks within a large area that includes Coleman, Eastland, Erath, Jack, McCulloch, Montague, Palo Pinto, Parker, Throckmorton, Wise, Young, and other counties. Before the general availability of oil and gas, underground coal mines near Thurber, Bridgeport, Newcastle, Strawn, and other points annually produced significant coal tonnages. Preliminary evaluations indicate substantial amounts of coal may remain in the North Central Texas area. The coal seams there are generally no more than 30 inches thick and are commonly covered by well-consolidated overburden. Ash and sulphur content are high. Beginning in 1979, two bituminous coal mine operations in North Central Texas — one in southern Coleman County and one in northwestern Erath County — produced coal to be used as fuel by the cement industry. Neither mine is currently operating.
In South Texas, bituminous coal occurs in the Eagle Pass district of Maverick County, and bituminous cannel coal is present in the Santo Tomas district of Webb County. The Eagle Pass area was a leading coal-producing district in Texas during the late 1800s and early 1900s. The bituminous coal in that area, which occurs in the Upper Cretaceous Olmos Formation, has a high ash content and a moderate moisture and sulfur content. According to reports, Maverick County coal beds range from four to seven feet thick.
The cannel coals of western Webb County occur near the Rio Grande in middle Eocene strata. They were mined for more than 50 years and used primarily as a boiler fuel. Mining ceased from 1939 until 1978, when a surface mine was opened 30 miles northwest of Laredo to produce cannel coal for use as fuel in the cement industry and for export. An additional mine has since been opened in that county. Tests show that the coals of the Webb County Santo Tomas district have a high hydrogen content and yield significant amounts of gas and oil when distilled. They also have a high sulfur content. A potential use might be as a source of various petrochemical products.
Coal deposits in the Trans-Pecos country of West Texas include those in the Cretaceous rocks of the Terlingua area of Brewster County, the Eagle Spring area of Hudspeth County, and the San Carlos area of Presidio County. The coal deposits in these areas are believed to have relatively little potential for development as a fuel. They have been sold in the past as a soil amendment (see LEONARDITE).
COPPER — Copper minerals have been found in the Trans-Pecos area of West Texas, in the Llano Uplift area of Central Texas, and in redbed deposits of North Texas. No copper has been mined in Texas during recent years, and the total copper produced in the state has been relatively small. Past attempts to mine the North Texas and Llano Uplift copper deposits resulted in small shipments.
Practically all the copper production in the state has been from the Van Horn–Allamoore district of Culberson and Hudspeth counties in the Trans-Pecos area. Chief output was from the Hazel copper-silver mine of Culberson County that yielded over 1 million pounds of copper during 1891–1947. Copper ores and concentrates from outside of Texas are processed at smelters in El Paso and Amarillo.
CRUSHED STONE — Texas is among the leading states in the production of crushed stone. Most production consists of limestone; other kinds of crushed stone produced in the state include basalt (trap rock), dolomite, granite, marble, rhyolite, sandstone, and serpentinite. Large tonnages of crushed stone are used as aggregate in concrete, as road material, and in the manufacture of cement and lime. Some is used as riprap, terrazzo, roofing chips, filter material, fillers, as well as other purposes.
DIATOMITE (DIATOMACEOUS EARTH) — Diatomite is a very lightweight siliceous material consisting of the remains of microscopic aquatic plants (diatoms). It is used chiefly as a filter and filler; other uses are for thermal insulation, as an abrasive, as an insecticide carrier, as a lightweight aggregate, and for other purposes. The diatomite was deposited in shallow, fresh-water lakes that were present in the High Plains during portions of the Pliocene and Pleistocene epochs. Deposits have been found in Armstrong, Crosby, Dickens, Ector, Hartley, and Lamb counties. No diatomite is mined in Texas.
DOLOMITE ROCK — Dolomite rock, which consists largely of the mineral dolomite (calcium-magnesium carbonate), commonly is associated with limestone in Texas. Areas in which dolomite rock occurs include Central Texas, the Callahan Divide, and parts of the Edwards Plateau, High Plains, and West Texas. Some of the principal deposits of dolomite rock are found in Bell, Brown, Burnet, Comanche, Edwards, El Paso, Gillespie, Lampasas, Mills, Nolan, Taylor, and Williamson counties. Dolomite rock can be used as crushed stone (although much of Texas dolomite is soft and not a good aggregate material), in the manufacture of lime, and as a source of magnesium.
FELDSPAR — Large crystals and crystal fragments of feldspar minerals occur in the Precambrian pegmatite rocks that crop out in the Llano Uplift area of Central Texas — including Blanco, Burnet, Gillespie, Llano, and Mason counties — and in the Van Horn area of Culberson and Hudspeth counties in West Texas. Feldspar has been mined in Llano County for use as roofing granules and as a ceramic material. Feldspar is currently mined in Burnet County for use as an aggregate.
FLUORSPAR — The mineral fluorite (calcium fluoride), which is known commercially as fluorspar, occurs in both Central and West Texas. In Central Texas, the deposits that have been found in Burnet, Gillespie, and Mason counties are not considered adequate to sustain mining operations. In West Texas, deposits have been found in Brewster, El Paso, Hudspeth, Jeff Davis, and Presidio counties. Fluorspar has been mined in the Christmas Mountains of Brewster County and processed in Marathon. Former West Texas mining activity in the Eagle Mountains district of Hudspeth County resulted in the production of approximately 15,000 short tons of fluorspar during the peak years of 1942–1950. No production has been reported in Hudspeth County since that period. Imported fluorspar is processed in Brownsville, Eagle Pass, El Paso, and Houston. Fluorspar is used in the steel, chemical, aluminum, magnesium, ceramics, and glass industries, and for various other purposes.
FULLER’S EARTH (see CLAY).
GOLD — No major deposits of gold are known in Texas. Small amounts have been found in the Llano Uplift region of Central Texas and in West Texas; minor occurrences have been reported on the Edwards Plateau and the Gulf Coastal Plain of Texas. Nearly all of the gold produced in the state came as a by-product of silver and lead mining at Presidio mine, near Shafter in Presidio County. Additional small quantities were produced as a by-product of copper mining in Culberson County and from residual soils developed from gold-bearing quartz stringers in metamorphic rocks in Llano County. No gold mining has been reported in Texas since 1952. Total gold production in the state from 1889–1952 amounted to more than 8,419 troy ounces, according to U.S. Bureau of Mines figures. Most of the production — at least 73 percent and probably more — came from the Presidio mine.
GRANITE — Granites in shades of red and gray and related intrusive igneous rocks occur in the Llano Uplift of Central Texas and in the Trans-Pecos country of West Texas. Deposits are found in Blanco, Brewster, Burnet, El Paso, Gillespie, Hudspeth, Llano, McCulloch, Mason, Presidio, and other counties. Quarries in Burnet, Gillespie, Llano, and Mason counties produce Precambrian granite for a variety of uses as dimension stone and crushed stone.
GRAPHITE — Graphite, a soft, dark-gray mineral, is a form of very high-grade carbon. It occurs in Precambrian schist rocks of the Llano Uplift of Central Texas, notably in Burnet and Llano counties. Crystalline-flake graphite ore formerly was mined from open pits in the Clear Creek area of western Burnet County and processed at a plant near the mine. The mill now occasionally grinds imported material. Uses of natural crystalline graphite are refractories, steel production, pencil leads, lubricants, foundry facings, and crucibles, as well as other purposes.
GRINDING PEBBLES (ABRASIVE STONES) — Flint pebbles, suitable for use in tube-mill grinding, are found in the Gulf Coastal Plain, where they occur in gravel deposits along rivers and in upland areas. Grinding pebbles are produced from Frio River terrace deposits near the McMullen–Live Oak county line, but the area is now part of the Choke Canyon Reservoir area.
GYPSUM — Gypsum is widely distributed in Texas. Chief deposits are bedded gypsum in the area east of the High Plains, in the Trans-Pecos country, and in Central Texas. It also occurs in salt-dome caprocks of the Gulf Coast. The massive, granular variety, which is known as rock gypsum, is the kind most commonly used by industry. Other varieties include alabaster, satin spar, and selenite.
Gypsum is one of the important industrial minerals in Texas. Bedded gypsum is produced from surface mines in Culberson, Fisher, Gillespie, Hardeman, Hudspeth, Kimble, Nolan, and Stonewall counties. Gypsum was formerly mined at Gyp Hill salt dome in Brooks County and at Hockley salt dome in Harris County. Most of the gypsum is calcined and used in the manufacture of gypsum wallboard, plaster, joint compounds, and other construction products. Crude gypsum is used chiefly as a retarder in portland cement and as a soil conditioner.
HELIUM — Helium is a very light, nonflammable, chemically inert gas. The U.S. Interior Department has ended its helium operation near Masterson in the Panhandle. The storage facility at Cliffside gas field near Amarillo and the 425-mile pipeline system will remain in operation until the government sells its remaining unrefined, crude helium. Helium is used in cryogenics, welding, pressurizing and purging, leak detection, synthetic breathing mixtures, and for other purposes.
IRON — Iron oxide (limonite, goethite, and hematite) and iron carbonate (siderite) deposits occur widely in East Texas, notably in Cass, Cherokee, Marion, and Morris counties, and also in Anderson, Camp, Harrison, Henderson, Nacogdoches, Smith, Upshur, and other counties. Magnetite (magnetic, black iron oxide) occurs in Central Texas, including a deposit at Iron Mountain in Llano County. Hematite occurs in the Trans-Pecos area and in the Llano Uplift of Central Texas. The extensive deposits of glauconite (a complex silicate containing iron) that occur in East Texas and the hematitic and goethitic Cambrian sandstone that crops out in the northwestern Llano Uplift region are potential sources of low-grade iron ore.
Limonite and other East Texas iron ores are mined from open pits in Cherokee and Henderson counties for use in the preparation of portland cement, as a weighting agent in well-drilling fluids, as an animal feed supplement, and for other purposes. East Texas iron ores also were mined in the past for use in the iron-steel industry.
KAOLIN (see CLAY).
LEAD and ZINC — The lead mineral galena (lead sulfide) commonly is associated with zinc and silver. It formerly was produced as a by-product of West Texas silver mining, chiefly from the Presidio mine at Shafter in Presidio County, although lesser amounts were obtained at several other mines and prospects. Deposits of galena also are known to occur in Blanco, Brewster, Burnet, Gillespie, and Hudspeth counties.
Zinc, primarily from the mineral sphalerite (zinc sulphide), was produced chiefly from the Bonanza and Alice Ray mines in the Quitman Mountains of Hudspeth County. In addition, small production was reported from several other areas, including the Chinati and Montezuma mines of Presidio County and the Buck Prospect in the Apache Mountains of Culberson County. Zinc mineralization also occurs in association with the lead deposits in Cambrian rocks of Central Texas.
LEONARDITE — Deposits of weathered (oxidized) low-Btu value bituminous coals, generally referred to as “leonardite,” occur in Brewster County. The name leonardite is used for a mixture of chemical compounds that is high in humic acids. In the past, material from these deposits was sold as soil conditioner. Other uses of leonardite include modification of viscosity of drill fluids and as sorbants in water-treatment.
LIGHTWEIGHT AGGREGATE (see CLAY, DIATOMITE, PERLITE, VERMICULITE).
LIGNITE — Almost all current coal production in Texas is located in the Tertiary-aged lignite belts that extend across the Texas Gulf Coastal Plain from the Rio Grande in South Texas to the Arkansas and Louisiana borders in East Texas. The Railroad Commission of Texas (RRC) reported that in 2011, Texas produced 45.6 million short tons of lignite from 15 mines. Cumulative production through 2011 was 1.58 billion short tons of lignite and coal. The U.S. Energy Information Administration (EIA) ranked Texas as the sixth-largest coal-producing state.
The near-surface lignite resources, occurring at depths of less than 200 feet in seams of three feet or thicker, are estimated at 23 billion short tons. Recoverable reserves of strippable lignite — those that can be economically mined under current conditions of price and technology — are estimated by the EIA to be 722 million short tons.
Additional lignite resources of the Texas Gulf Coastal Plain occur as deep-basin deposits. Deep-basin resources, those that occur at depths of 200 to 2,000 feet in seams of five feet or thicker, are comparable in magnitude to near-surface resources. The deep-basin lignites are a potential energy resource that conceivably could be utilized by in situ (in place) recovery methods such as underground gasification.
As with bituminous coal, lignite production was significant prior to the general availability of oil and gas. Remnants of old underground mines are common throughout the area of lignite occurrence. Large reserves of strippable lignite have again attracted the attention of energy suppliers, and Texas is now the nation’s sixth leading producer of coal, 99 percent of it lignite. Twelve large strip mines are now producing lignite that is burned for mine-mouth electric-power generation, and additional mines are planned. Mines are located in Atascosa, Franklin, Freestone, Harrison, Hopkins, Leon, Limestone, McMullen, Milam, Panola, Robertson, Rusk, and Titus counties.
LIME MATERIAL — Limestones, which are abundant in some areas of Texas, are heated to produce lime (calcium oxide) at a number of plants in the state. High-magnesium limestone and dolomite are used to prepare lime at a plant in Burnet County. Other lime plants are located in Bexar, Bosque, Comal, Hill, Johnson, and Travis counties. Lime production captive to the kiln’s operator occurs in several Texas counties. Lime is used in soil stabilization, water purification, paper and pulp manufacture, metallurgy, sugar refining, agriculture, construction, removal of sulfur from stack gases, and for many other purposes.
LIMESTONE (see also BUILDING STONE) — Texas is one of the nation’s leading producers of limestone, which is quarried in more than 60 counties. Limestone occurs in nearly all areas of the state with the exception of most of the Gulf Coastal Plain and High Plains. Although some of the limestone is quarried for use as dimension stone, most of the output is crushed for uses such as bulk building materials (crushed stone, road base, concrete aggregate), chemical raw materials, fillers or extenders, lime and portland cement raw materials, agricultural limestone, and removal of sulfur from stack gases.
MAGNESITE — Small deposits of magnesite (natural magnesium carbonate) have been found in Precambrian rocks in Llano and Mason counties of Central Texas. At one time, there was small-scale mining of magnesite in the area; some of the material was used as agricultural stone and as terrazzo chips.Magnesite also can be calcined to form magnesia, which is used in metallurgical furnace refractories and other products.
MAGNESIUM — On the Texas Gulf Coast in Brazoria County, magnesium chloride is extracted from sea water at a plant in Freeport and used to produce magnesium compounds and magnesium metal. During World War II, high-magnesium Ellenburger dolomite rock from Burnet County was used as magnesium ore at a plant near Austin.
MANGANESE — Deposits of manganese minerals, such as braunite, hollandite, and pyrolusite, have been found in several areas, including Jeff Davis, Llano, Mason, Presidio, and Val Verde counties. Known deposits are not large. Small shipments have been made from Jeff Davis, Mason, and Val Verde counties, but no manganese mining has been reported in Texas since 1954.
MARBLE — Metamorphic and sedimentary marbles suitable for monument and building stone are found in the Llano Uplift and nearby areas of Central Texas and the Trans-Pecos area of West Texas. Gray, white, black, greenish black, light green, brown, and cream-colored marbles occur in Central Texas in Burnet, Gillespie, Llano, and Mason counties. West Texas metamorphic marbles include the bluish-white and the black marbles found southwest of Alpine in Brewster County and the white marble from Marble Canyon north of Van Horn in Culberson County. Marble can be used as dimension stone, terrazzo, and roofing aggregate, and for other purposes.
MERCURY (QUICKSILVER) — Mercury minerals, chiefly cinnabar, occur in the Terlingua district and nearby districts of southern Brewster and southeastern Presidio counties. Mining began there about 1894, and from 1905–1935, Texas was one of the nation’s leading producers of quicksilver. Following World War II, a sharp drop in demand and price, along with depletion of developed ore reserves, caused abandonment of all the Texas mercury mines.
With a rise in the price, sporadic mining took place between 1951–1960. In 1965, when the price of mercury moved to a record high, renewed interest in the Texas mercury districts resulted in the reopening of several mines and the discovery of new ore reserves. By April 1972, however, the price had declined and the mines have reported no production since 1973.
MICA — Large crystals of flexible, transparent mica minerals in igneous pegmatite rocks and mica flakes in metamorphic schist rocks are found in the Llano Uplift area of Central Texas and the Van Horn area of West Texas. Most Central Texas deposits do not meet specifications for sheet mica, and although several attempts have been made to produce West Texas sheet mica in Culberson and Hudspeth counties, sustained production has not been achieved. A mica quarry operated for a short time in the early 1980s in the Van Horn Mountains of Culberson and Hudspeth counties to mine mica schist for use as an additive in rotary drilling fluids.
MOLYBDENUM — Small occurrences of molybdenite have been found in Burnet and Llano counties, and wulfenite, another molybdenum mineral, has been noted in rocks in the Quitman Mountains of Hudspeth County. Molybdenum minerals also occur at Cave Peak north of Van Horn in Culberson County, in the Altuda Mountain area of northwestern Brewster County, and in association with uranium ores of the Gulf Coastal Plain.
PEAT — This spongy organic substance forms in bogs from plant remains. It has been found in the Gulf Coastal Plain in several localities including Gonzales, Guadalupe, Lee, Milam, Polk, and San Jacinto counties. There has been intermittent, small-scale production of some of the peat for use as a soil conditioner.
PERLITE — Perlite, a glassy igneous rock, expands to a lightweight, porous mass when heated. It can be used as a lightweight aggregate, filter aid, horticultural aggregate, and for other purposes. Perlite occurs in Presidio County, where it has been mined in the Pinto Canyon area north of the Chinati Mountains. No perlite is currently mined in Texas, but perlite mined outside of Texas is expanded at plants in Bexar, Dallas, El Paso, Guadalupe, Harris, and Nolan counties.
PHOSPHATE — Rock phosphate is present in Paleozoic rocks in several areas of Brewster and Presidio counties in West Texas and in Central Texas, but the known deposits are not large. In Northeast Texas, sedimentary rock phosphate occurs in thin conglomeratic lenses in Upper Cretaceous and Tertiary rock units; possibly some of these low-grade phosphorites could be processed on a small scale for local use as a fertilizer. Imported phosphate rock is processed at a plant in Brownsville.
POTASH — The potassium mineral polyhalite is widely distributed in the subsurface Permian Basin of West Texas and has been found in many wells in that area. During 1927–1931, the federal government drilled a series of potash-test wells in Crane, Crockett, Ector, Glasscock, Loving, Reagan, Upton, and Winkler counties. In addition to polyhalite, which was found in all of the counties, these wells revealed the presence of the potassium minerals carnallite and sylvite in Loving County and carnallite in Winkler County. The known Texas potash deposits are not as rich as those in the New Mexico portion of the Permian Basin and have not been developed.
PUMICITE (VOLCANIC ASH) — Deposits of volcanic ash occur in Brazos, Fayette, Gonzales, Karnes, Polk, Starr, and other counties of the Texas Coastal Plain. Deposits also have been found in the Trans-Pecos area, High Plains, and in several counties east of the High Plains. Volcanic ash is used to prepare pozzolan cement, cleansing and scouring compounds, and soaps and sweeping compounds; as a carrier for insecticides, and for other purposes. It has been mined in Dickens, Lynn, Scurry, Starr, and other counties.
QUICKSILVER (see MERCURY).
RARE-EARTH ELEMENTS and METALS — The term, “rare-earth elements,” is commonly applied to elements of the lanthanide group (atomic numbers 57 through 71) plus yttrium. Yttrium, atomic number 39 and not a member of the lanthanide group, is included as a rare-earth element because it has similar properties to members of that group and usually occurs in nature with them. The metals thorium and scandium are sometimes termed “rare metals” because their occurrence is often associated with the rare-earth elements.
The majority of rare-earth elements are consumed as catalysts in petroleum cracking and other chemical industries. Rare earths are widely used in the glass industry for tableware, specialty glasses, optics, and fiber optics. Cerium oxide has growing use as a polishing compound for glass, gem stones, cathode-ray tube faceplates, and other polishing. Rare earths are alloyed with various metals to produce materials used in the aeronautic, space, and electronics industries. The addition of rare-earth elements may improve resistance to metal fatigue at high temperatures, reduce potential for corrosion, and selectively increase conductivity and magnetism of the metal.
Various members of this group, including thorium, have anomalous concentrations in the rhyolitic and related igneous rocks of the Quitman Mountains and the Sierra Blanca area of Trans-Pecos.
SALT (SODIUM CHLORIDE) (see also BRINES) — Salt resources of Texas are virtually inexhaustible. Enormous deposits occur in the subsurface Permian Basin of West Texas and in the salt domes of the Gulf Coastal Plain. Salt also is found in the alkali playa lakes of the High Plains, the alkali flats or salt lakes in the Salt Basin of Culberson and Hudspeth counties, and along some of the bays and lagoons of the South Texas Gulf Coast.
Texas is one of the leading salt-producing states. Rock salt is obtained from underground mines in salt domes at Grand Saline in Van Zandt County and Hockley Dome in Harris County. Salt is produced from rock salt and by solution mining as brines from wells drilled into the underground salt deposits.
SAND, INDUSTRIAL — Sands used for special purposes, due to high silica content or to unique physical properties, command higher prices than common sand. Industrial sands in Texas occur mainly in the central Gulf Coastal Plain and in North Central Texas. They include abrasive, blast, chemical, engine, filtration, foundry, glass, hydraulic-fracturing (propant), molding, and pottery sands. Recent production of industrial sands has been from Atascosa, Colorado, Hardin, Harris, Liberty, Limestone, McCulloch, Newton, Smith, Somervell, and Upshur counties.
SAND and GRAVEL (CONSTRUCTION) — Sand and gravel are among the most extensively utilized resources in Texas. Principal occurrence is along the major streams and in stream terraces. Sand and gravel are important bulk construction materials, used as railroad ballast, base materials, and for other purposes.
SANDSTONE — Sandstones of a variety of colors and textures are widely distributed in a number of geologic formations in Texas. Some of the sandstones have been quarried for use as dimension stone in El Paso, Parker, Terrell, Ward, and other counties. Crushed sandstone is produced in Freestone, Gaines, Jasper, McMullen, Motley, and other counties for use as road-building material, terrazzo stone, and aggregate.
SERPENTINITE — Several masses of serpentinite, which formed from the alteration of basic igneous rocks, are associated with other Precambrian metamorphic rocks of the Llano Uplift. The largest deposit is the Coal Creek serpentinite mass in northern Blanco and Gillespie counties from which terrazzo chips have been produced. Other deposits are present in Gillespie and Llano counties. (The features that are associated with surface and subsurface Cretaceous rocks in several counties in or near the Balcones Fault Zone and that are commonly known as “serpentine plugs” are not serpentine at all, but are altered igneous volcanic necks and pipes, and mounds of altered volcanic ash — palagonite — that accumulated around the former submarine volcanic pipes.)
SHELL — Oyster shells and other shells in shallow coastal waters and in deposits along the Texas Gulf Coast have been produced in the past chiefly by dredging. They were used to a limited extent as raw material in the manufacture of cement, as concrete aggregate and road base, and for other purposes. No shell has been produced in Texas since 1981.
SILVER — During the period 1885–1952, the production of silver in Texas, as reported by the U.S. Bureau of Mines, totaled about 33 million troy ounces. For about 70 years, silver was the most consistently produced metal in Texas, although always in moderate quantities. All of the production came from the Trans-Pecos country of West Texas, where the silver was mined in Brewster County (Altuda Mountain), Culberson and Hudspeth counties (Van Horn Mountains and Van Horn–Allamoore district), Hudspeth County (Quitman Mountains and Eagle Mountains), and Presidio County (Chinati Mountains area, Loma Plata mine, and Shafter district).
Chief producer was the Presidio mine in the Shafter district, which began operations in the late 1800s, and, through September 1942, produced more than 30 million ounces of silver — more than 92 percent of Texas’ total silver production. Water in the lower mine levels, lean ores, and low price of silver resulted in the closing of the mine in 1942. Another important silver producer was the Hazel copper-silver mine in the Van Horn–Allamoore district in Culberson County, which accounted for more than 2 million ounces.
An increase in the price of silver in the late 1970s stimulated prospecting for new reserves, and exploration began near the old Presidio mine, near the old Plata Verde mine in the Van Horn Mountains district, at the Bonanza mine in the Quitman Mountains district, and at the old Hazel mine. A decline in the price of silver in the early 1980s, however, resulted in reduction of exploration and mine development in the region. The recent rise in value of silver has sparked new interest in the Shafter mining district of West Texas.
SOAPSTONE (see TALC and SOAPSTONE).
SODIUM SULFATE (SALT CAKE) — Sodium sulfate minerals occur in salt beds and brines of the alkali playa lakes of the High Plains in West Texas. In some lakes, the sodium sulfate minerals are present in deposits a few feet beneath the lakebeds. Sodium sulfate also is found in underground brines in the Permian Basin. Current production is from brines and dry salt beds at alkali lakes in Gaines and Terry counties. Past production was reported in Lynn and Ward counties. Sodium sulfate is used chiefly by the detergent and paper and pulp industries. Other uses are in the preparation of glass and other products.
STONE (see BUILDING STONE and CRUSHED STONE).
STRONTIUM — Deposits of the mineral celestite (strontium sulfate) have been found in a number of places, including localities in Brown, Coke, Comanche, Fisher, Lampasas, Mills, Nolan, Real, Taylor, Travis, and Williamson counties. Most of the occurrences are very minor, and no strontium is currently produced in the state.
SULFUR — Texas is one of the world’s principal sulfur-producing areas. The sulfur is mined from deposits of native sulfur, and it is extracted from sour (sulfur-bearing) natural gas and petroleum. Recovered sulfur is a growing industry and accounted for approximately 60 percent of all 1987 sulfur production in the United States, but only approximately 40 percent of Texas production. Native sulfur is found in large deposits in the caprock of some of the salt domes along the Texas Gulf Coast and in some of the surface and subsurface Permian strata of West Texas, notably in Culberson and Pecos counties.
Native sulfur obtained from the underground deposits is known as Frasch sulfur, so-called because of Herman Frasch, the chemist who devised the method of drilling wells into the deposits, melting the sulfur with superheated water, and forcing the molten sulfur to the surface. Most of the production now goes to the users in molten form.
Frasch sulfur is produced from only one Gulf Coast salt dome in Wharton County and from West Texas underground Permian strata in Culberson County. Operations at several Gulf Coast domes have been closed in recent years. During the 1940s, acidic sulfur earth was produced in the Rustler Springs district in Culberson County for use as a fertilizer and soil conditioner. Sulfur is recovered from sour natural gas and petroleum at plants in numerous Texas counties.
Sulfur is used in the preparation of fertilizers and organic and inorganic chemicals, in petroleum refining, and for many other purposes.
TALC and SOAPSTONE — Deposits of talc are found in the Precambrian metamorphic rocks of the Allamoore area of eastern Hudspeth and western Culberson counties. Soapstone, containing talc, occurs in the Precambrian metamorphic rocks of the Llano Uplift area, notably in Blanco, Gillespie, and Llano counties. Current production is from surface mines in the Allamoore area. Talc is used in ceramic, roofing, paint, paper, plastic, synthetic rubber, and other products.
TIN — Tin minerals have been found in El Paso and Mason counties. Small quantities were produced during the early 1900s in the Franklin Mountains north of El Paso. Cassiterite (tin dioxide) occurrences in Mason County are believed to be very minor. The only tin smelter in the United States, built at Texas City by the federal government during World War II and later sold to a private company, processes tin concentrates from ores mined outside of Texas, tin residues, and secondary tin-bearing materials.
TITANIUM — The titanium mineral rutile has been found in small amounts at the Mueller prospect in Jeff Davis County. Another titanium mineral, ilmenite, occurs in sandstones in Burleson, Fayette, Lee, Starr, and several other counties. Deposits that would be considered commercial under present conditions have not been found.
TRAP ROCK (see BASALT).
TUNGSTEN — The tungsten mineral scheelite has been found in small deposits in Gillespie and Llano counties and in the Quitman Mountains in Hudspeth County. Small deposits of other tungsten minerals have been prospected in the Cave Peak area north of Van Horn in Culberson County.
URANIUM — Uranium deposits were discovered in the Texas Coastal Plain in 1954 when abnormal radioactivity was detected in the Karnes County area. A number of uranium deposits have since been discovered within a belt of strata extending more than 250 miles from the middle Coastal Plain southwestward to the Rio Grande.
Various uranium minerals also have been found in other areas of Texas, including the Trans-Pecos, the Llano Uplift, and the High Plains. With the exception of small shipments from the High Plains during the 1950s, all the uranium production in Texas has been from the Coastal Plain. Uranium has been obtained from surface mines extending from northern Live Oak County, southeastern Atascosa County, across northern Karnes County, and into southern Gonzales County. Uranium is produced by in-situ leaching, brought to the surface through wells, and stripped from the solution at recovery operations.
In 1999, uranium mining shut down because of decreased value and demand. Production resumed in Texas in late 2004, when inventories were depleted and market prices rose to economic levels that allowed resumption of production. A total of 1.38 million pounds (606.5 tons) of eU3O8 was produced in South Texas in 2007.
VERMICULITE — Vermiculite, a mica-like mineral that expands when heated, occurs in Burnet, Gillespie, Llano, Mason, and other counties in the Llano Uplift region. It has been produced at a surface mine in Llano County. Vermiculite, mined outside of Texas, is exfoliated (expanded) at plants in Dallas, Houston, and San Antonio. Exfoliated vermiculite is used for lightweight concrete aggregate, horticulture, insulation, and other purposes.
VOLCANIC ASH (see PUMICITE).
ZEOLITES — The zeolite minerals clinoptilolite and analcime occur in Tertiary lavas and tuffs in Brewster, Jeff Davis, and Presidio counties in West Texas. Clinoptilolite also is found associated with Tertiary tuffs in the southern Texas Coastal Plain, including deposits in Karnes, McMullen, and Webb counties, and currently is produced in McMullen County. Zeolites, sometimes called “molecular sieves,” can be used in ion-exchange processes to reduce pollution, as a catalyst in oil cracking, in obtaining high-purity oxygen and nitrogen from air, in water purification, and for many other purposes.
ZINC (see LEAD and ZINC).