Surface Versus Mineral Ownership Much of the individually owned minerals in the United States have resulted fromoriginalU.S.govern- ment patents and land grants to institutions and private entities. Originally, most landownership con- cerned land in its entirety; this type of ownership was called “feeownership” and implied both surface own - ership and mineral ownership all the way down to the center of the Earth. Subsequent land transactions have subdivided fee ownership into smaller tracts as well as separating (“severing”) surface ownership from mineral ownership. It is also com- mon to find private surface owner- ship overlying government-owned mineral ownership. The reverse is rare. Sometimes the government- owned minerals in areas of extensive mining activity have been inadver- tently extracted because of confu- sion as to the rightful owner. Mineral ownership can be nebu- lous andis not as closely defined and monitored in some situations as is surface ownership. As a result, even basic property tax obligations may be ignored through misunderstand- ings so that mineral property is often “orphaned” by rightful owners and can be secured by more knowledge- able individuals by paying the taxes due or otherwise convincing the lo- cal property assessor that they are in possession of the mineral owner- ship. The folklore of mineral prop- erty ownershipisfilled with stories of the incidental property transfer that leads to vast wealth for the acquirer through subsequent mineral extrac- tion. Although surface property has been known to escalate to hundreds or even thousands of times its initial value, mineral ownership can result in a million or more times its original value through proceeds from miner- als extraction. Yet the management of mineral ownership is often not of primary importance to the individ- ual because its value is frequently misunderstood. The separation of surface from mineral owner- ship often creates a unique set of problems. If min- eral owners have the opportunity to have their miner- als extracted, the consequence to the surface owner must be considered. In some states, the mineral owner has “primacy” such that reasonable access to the min- erals must be provided; the surface owner must be compensated for damages resulting from mineral- extraction activities. In some areas where mineral 748 • Mineral resource ownership Global Resources This is a gas well on the Crow Nation American Indian reservation in Montana. How- ever, the government—and not the tribe—possesses mineral rights because the land is di- vided between aboveground andbelowgroundownership,acommonprocess in the Ameri- can West. (Reuters/Landov) extraction is not feasible from surface operations, such as in urban or environmentally sensitive sites, the fate of mineral ownership may be determined in courts of law. Mineral ownership in many remote areas across the United States has minimal value because no iden- tifiable commercial minerals are evident, or, if they are present, they are too far from markets to have value. In areas of extensive mineral extraction, such as traditional mining provinces or in oil and gas fields, mineral ownership isclosely protected and itssubdivi- sion complicated. In these areas, the severance of mineral types, depths, and locations is common. For example, if multiple coal deposits exist from the sur- face to depth, the individual deposits may be identi- fied as to ownership. In southern Illinois, for exam- ple, the many shallow coal deposits are exclusively reserved for mining, while deeper coal deposits are used for coal-bedmethane extraction through drilled wells. In oil and gas areas, producing formations are identified and may be separated as to ownership. Fre- quently, a shallow oil and gaszone may be included in a lease along with deeper zones. A time limit is im- posed on the development of the shallow zone such that it reverts to the mineral owner if not exploited. Oil and gas developers may be surprised to learn that they cannot exploit the shallow zone even after com- mitting funds to it. Individual minerals may be sepa- rated as well, withcoal,oil, natural gas, sulfur,metallic minerals, and industrial minerals being identified as individual entities. Transactions and Appraisals Mineral ownership can be exchanged through like- kind trades or exchanges for virtually anything of value. The appraisal of mineral ownership is a fre- quent activity but involves specialized training. Since many estates contain mineral ownership, the payment of estatetaxes depends on an appraisal of themineral ownership. As compared with surface ownership, which may often be appraised through comparable sales, mineral transactions may be so rare in some ar- eas as to have no standard of comparison. This fact places an additional burden on the appraiser in arriv- ing at an accurate evaluation. Mineral ownership may be appraised by calculat- ing a discounted present value of future revenues from mineral exploitation. If active mineral extrac - tion operations are under way onatract,projection of these activities into the future may be relatively accu - rate. If assumptions of minerals pricingandoperating expenses are accurate, the appraisal of mineral own- ership may well depend on discounted present value calculations. Determination of Ownership The determination of mineral ownership is similar to determination of surface ownership. Title searches are made by professionals who execute a study of the ownership history of a tract of mineral ownership. A chain of title is made to determine if any “clouds” on the titleare indicated and to recommend remedies to these deficiencies. A title search may be very simple if the ownership is created from the original U.S. pat- ent. It can be extremely complicated if the mineral ownership has been involved in numerous transac- tions, its ownership subdivided, and its minerals sev- ered. Nomineral extraction operation, such as mining or oil and gas drilling, is begun without a reasonable title opinion. Otherwise, the mineral exploitation is at-risk as to the payment of proceeds to the right- ful owner as well as lawsuits from maligned mineral owners. Disputes involving mineral property ownership are common and include boundary disagreements, geo- logical misinterpretations, and depth disputes. Even the classification of minerals sometimes involves liti- gation. Mineral disputes can also be settled by me- diation or arbitration in lieu of court appearances. The nature of dispute settlement may depend on the language agreed upon by parties in earlier transac- tions. Wealth is created by mineral ownership transac- tions as discussed above, where trades may increase the value of the ownership. The greatest amount of wealth enhancement, however, usually results when a royalty from minerals extraction is negotiated. If the mineral deposit is large and valuable, the min- eral owner can realize millions of dollars in royalties from mineral extraction. As an example, a coal de- posit 4 meters in thickness contains about 18,000 metric tons per hectare. If a royalty is negotiated to be $3 per metric ton, the proceeds to the mineral owner are $54,000 per hectare. Only in developed suburban areas will surface property values be greater. Even greater wealth can be generated in areas where solid minerals as well as oil and gas can be exploited. This frequently occurs in the Appalachian Basin in the eastern United States as well as in the Rocky Mountains. Global Resources Mineral resource ownership • 749 Mineral Leasing If mineral leasing is desired, there are guidelines that govern most lease transactions.Mineral leases involve a mineral owner, called a lessor, and a mineral opera- tor or intermediary, called the lessee. A mineral lease usually contains a primary term, bonus, and royalty rate. The term is the time extent of the lease agree- ment and can vary from one year to as much as ten years. Multiple-year leases mayalso involve delay rent- als, or annual rental fees to retain the lease. Others are paid up at the outset of leasing, meaning that no delay rentals areduefor the primary termofthelease. Some leases also have extensions past the primary term. Oil and gas leasesusually specify thata lease can be held past the expiration of the primary term if commercial production has been established and is sustained with nocessationover a term,usually ninety days. Stone and coalminingleases do not usually have a held-by-production clause, but rather provide for protection of future mining activity by using exten- sions to the primary term that can be unilaterally re- quested by the lessee with suitable advance notice to the lessor. Lease bonuses are defined as the amount of consid- eration due to the lessor at the time of lease execu- tion. This amount varies with the value of the lease, and it may be as little as zero or as much as thousands of dollars per hectare. In places where an oil and gas “play” is under way, lease bonuses can be in the thou- sands of dollars for land parcels no larger than town lots. On the other hand, tracts intended for pure ex- ploration drilling (“wildcats”) may secure lease bo- nuses of only one to five dollars per hectare if any- thing. Governmental agencies, such as the Bureau of Land Management in the U.S. Department of the In- terior, often demand larger than average bonuses be- cause they may control the fate of mineral develop- ment. The most important part of a mineral lease is the royalty. This is the income accruing to the mineral owner over the productive life of the lease. Royalty ar- rangements can beas varied asthere are minerals and areas ofthe UnitedStates, butthese arrangements of- ten involvea percentage of the minerals produced. In times past, the royalty was paid “in-kind,” meaning that the royalty owner was issued the proportionate share of the mineral in the same form as the operator and could market or keep it for domestic use as de - sired. Modern operating practice, which usually in - cludes long-term contracts for the marketing of min - erals, provides the royalty owner with a percentage of the selling price. Royalty percentages vary from 2 per- cent of thesellingprice in the rock and stone industry to as highas 25 percent or even30 percent in offshore oil and gas operations. Coal mining has royalty rates in the 5 percent to 10 percent range. In most cases, there has been a tendency for royalty percentages to increase over the past several decades. Another trend in mineral leases is for the royalty interest to bear cer- tain expenses of operation, particularly if a very large development cost is necessary to jump-start the min- eral exploitation. These are usually fees involved in re- fining or marketing the product. Measurement ofthe bulk mineral or even the basis for its pricing are often the cause of litigation where the royalties are based on selling price. For example, if the mineral commodity is sold to an affiliate, a “sweetheart price” lower than fair-market value may result. Endless disputes overproperty boundariesand language in mineral conveyance documents, leases, and deeds have given rise to a legal specialty in min- eral law and even to subspecialties such as oil and gas law. Certain clauses in leases protect the lessor from a mineral operator making a halfhearted effort to de- velop the lease. Onesuchclauserequires timely devel- opment of the leased tract either through continuity of production or, in the case of oil and gas develop- ment, the steady drilling of new wells to prevent forfei- ture of the lease. Development Priorities The question of mineral development priority fre- quently arises in areas having multiple mineral re- sources. Interference is minimized if the minerals in question can be recovered simultaneously. However, there are situations where theexploitation of a partic- ular mineral commodity must wait until another is fully exploited. Examples of this include the extrac- tion of near-surface minerals or the recovery of deep minerals where the exploitation of one would com- promise the exploitation of the other. Even relatively simple situations can result in ex- pensive and time-consuming litigation.Somemineral ownership assignment documentsspecify the “superi- ority” of certain mineral commodities and place pri- orities on their extraction. If the purchase of mineral ownership iscontemplated, the title search should re - veal whether exploitation priorities are specified. As mentioned above, disputes involving mineral owner - 750 • Mineral resource ownership Global Resources ship and minerals development have been and still are quite common for a number of practical reasons. Inaccuracies in land surveying, the evolution of geo- logic nomenclature, the shifting of streambeds, and dishonest transactions all create discord. Attorneys and experts in mineral development team to con- vince regulatory agencies, courts of law, and media- tors that the evidence supports their client’s claims. Sometimes, the evidenceisclear-cut. Most often,how- ever, a judgment decision is necessary where the evi- dence is far from perfect. Measurements and Disputes A classic type of dispute in oil and gas development involves the drilling of wells to drain underneath an adjacent tract. In the past, innumerable disputes con- cerned this “hot oil” problem. Modern drilling tech- nology, with its downhole drilling motors, permits drilling a verticalwellandthen directing it to the hori- zontal in a prescribed radius of curvature, such that a well could be 1,500 meters in depth and its bottom could be 600 meters laterally from its surface location. These wells are “surveyed” by using dip and azimuth tools in the drillhole to pinpoint the location of the bottom of the hole at any time, thus preventing a dis- pute over whether adjacent property rights are being violated. Downhole depth surveys also ensure that the oil or gas well has not penetrated a lower zone that is sev- ered from upper zones in a multiple-pay area. Instru- ments can be used to determine whether an oil or gas zone is being produced from any zone downhole. Both the potential inaccuracy of measuring devices and the possibility of dishonest measurement of bulk commodities typify the problems confronting a min- eral owner seeking a royalty payment. The production of solid bulk minerals such as coal is determined by weighing a truck or railroad car on a large drive- through scale, then loading it and subtracting its “tare” weight to determine the amount of solid mate- rial being transported. Liquid commodities such as oil are measured by flow meters or storage tank mea- surements. Gaseous commodities such as natural gas are measured by rotating meters or orifice plates. All these measurement systems contain inherent inaccu- racies such that the systems must be “proved,” or cali- brated against a measurement standard at regular in- tervals. The measurement of solid or liquid minerals in floating vessels such as barges is made by displace - ment of the barge in water. This is done by scaling its draft in water in an unloaded and loaded condition. The draft per weight of cargo is then converted into tonnage. Timber Rights and Water Rights Other types of property rights may be seen in certain parts of the United States. Examples of these rights are timber ownership and the right to use surface or underground water resources. The ownership of water resources is particularly important in the more arid areas of the Southwest, and legal battles are fre- quently fought over access to potable and irrigation water. Timber ownership is frequently bought and sold in the southeast and northwest areas of the United States. In areas where tree harvesting is a recurring endeavor, the right to grow timber is valuable and is often at odds with the extractive industries. Charles D. Haynes Further Reading Barberis, Daniéle. Negotiating Mining Agreements: Past, Present, and Future Trends. Boston: Kluwer Law In- ternational, 1998. Braunstein, Michael. Mineral Rights on the Public Do- main. Cincinnati, Ohio: Anderson, 1987. Hughes, Richard V. Oil Property Valuation.2drev.ed. Huntington, N.Y.: R. E. Krieger, 1978. Lowe, John S. Oil and Gas Law in a Nutshell. 4th ed. St. Paul, Minn.: Thomson/West, 2003. _______, et al. Cases and Materials on Oil and Gas Law. 4th ed. St. Paul, Minn.: West Group, 2002. Maley, Terry S. MineralLaw. 6th ed.Boise,Idaho: Min- eral Land Publications, 1996. Mayer, Carl J., and George A. Riley. Public Domain, Pri- vate Dominion: A History of Public Mineral Policy in America. San Francisco: Sierra Club Books, 1985. Muchow, David J., and William A. Mogel, eds. Energy Law and Transactions. 6 vols. New York: Lexis, 1990- 2001. Otto, James, et al. Mining Royalties: A Global Study of Their Impact on Investors, Government, and Civil Soci- ety. Washington, D.C.: World Bank, 2006. Thompson, Robert S., and John D. Wright.Oil Property Evaluation. Golden, Colo.: Thompson-Wright,1984. See also: Mineral Leasing Act; Oil and natural gas drilling and wells; Oil industry; Takings law and emi - nent domain; Timber industry; Water rights. Global Resources Mineral resource ownership • 751 Mineral resource use, early history of Categories: Historical events and movements; social, economic, and political issues Beginning with theStoneAge, people have usedminer- als both to forge the material part of civilization and to express their artistic natures. Background There were inventors and great thinkers in the family tree of humankind many thousands of years before recorded history began. One of them was the first to use a stoneasa tool, which wasanimportant step inthe ascent of humankind because it gave people greater control over their world and their lives. Someone was the first to make a clay pot,thefirsttofindausefor tar, the first to beat native copper into a useful shape. Somewhere in Mesopotamia in the seventh millen- nium b.c.e., someone inventedthekiln. A kiln is afur- nace that retains and focuses a fire’s heat and allows the air flow to be controlled. The kiln technology of the eastern Mediterranean, Mesopotamia, and Egypt was unsurpassed, and it was there that production techniques for pottery, bricks, cement, glass, copper, and iron were first mastered. Stone Tools The oldest stone tools were crude and were made from whatever rocks were at hand. Later tools were made from stones chosen because they could be shaped by chipping and retain a sharp edge. Flints, cherts, and jaspers were among the most common stones used. Obsidian is more brittle than flint, but its edge can be made very sharp. When it was available and there was someone skilled enough to work it, ob- sidian was preferred for cutting tools. To shape a stone by chipping, a second stone may be used to strike glancing blows along the edge of the first stone. Common stone tools include hand axes, scrapers, flint knives, and awls (used to make holes in hides). Stone points were fastened to spears and ar- rows. Sickles to cut grain were made by setting sharp stone chips into wooden handles. A hollow can be formed in a stone by pecking with a hard sharp rock. Stone bowls, lamps, and traylike grindstones were made with this procedure from limestone, sandstone, granite, and basalt. (Grainwas ground by placing it in the grindstone and then rubbing it with a smaller handheld stone.) Building with Stone Because of the relative ease with which limestone and sandstone can beshaped,they are often used inbuild- ings. Granite is more durable but is harder to shape. Granite is formed from an underground mass of mol- ten rock that cools very slowly. Limestone and sand- stone are sedimentary rocks. Sediments turn to rock as the pressure of overlying layers squeezes waterfrom between the sediment particles. As the water is driven out, compounds dissolved in the water come out of solution and cement the sediment particles together. Calcite (calcium carbonate), silica (silicon dioxide) and hematite (iron oxide) are typical cementing agents. Limestone is mostly calcium carbonate. It occa- sionally is precipitated asa shallow seaevaporates, but more oftenit is built up from shellsof dead sea organ- isms. A limestonelike sediment containing a large fraction of calcium magnesium carbonate is called do- lomite and is a little harder than limestone. Lime- stone and dolomite subjected to sufficient heat and pressure become marble. With the passage of time, people became profi- cient at quarrying, shaping, and moving stone. The great pyramid of Khufu was constructed about 2600 b.c.e. It is 50 percent taller than the Statue of Liberty and is estimated to contain 2,300,000 stone blocks weighing anaverage of 2.3metric tons each. The core is made from huge yellowish limestone blocks from a nearby quarry, while the outer face and the inner pas- sageways are of a finer limestone brought from far- ther away. Khufu’s burial chamber lies deep within the pyramid and is built of granite from Asw3n. The leaning tower of Pisa, another fine example of early stone construction, was begun in 1174 c.e., more than three thousand years after the construc- tion of the great pyramid. The tower is constructed of white marble andhas colored marble inlayson the ex- terior. Its walls are nearly 4 meters thick at the base and taper to about half that at the top, 56 meters above the ground. In spiteof its pronounced tilt,itis a beautiful structure of arches and columns. Cement Gypsum is a soft rock that forms as a precipitate when a restricted body of seawater evaporates. Chemically, it is hydrous calcium sulfate. (“Hydrous” means that 752 • Mineral resource use, early history of Global Resources water molecules are incorporated into the mineral’s crystal structure.) If powdered and heatedtodrive off its water content, gypsum becomes the basic ingredi- ent of mortar. The Egyptians used gypsum mortar in building the pyramids. When limestone is heated in a kiln, carbon dioxide is driven off, leaving quicklime (calcium oxide). If clayeylimestoneisused, the quick- lime will contain large amounts of silica and alumina. This mix is called hydraulic lime. Adding water to hy- draulic lime produces a cement that will set and harden even underwater by forming calcium silicates and aluminates. The Romans produced a hydraulic lime mortar called pozzolana by combining quick - lime with sand and powdered volcanic tuff mined near the Italian town of Pozzuoli. Pozzolana was used in the construction of the Colosseum at Rome. Building with Brick Construction stone is rare in the fertile land beside the Euphrates, so the ancient Mesopotamians built with bricks. Ruins at Ur of the Chaldees have yielded both burned and unburned bricks that are five thou- sand years old. Clay suitable for making bricks is found throughout the world. Clay particles are very Global Resources Mineral resource use, early history of • 753 The Sumerian temple of Ur, in present-day Iraq, is an early example of the use of brick, a by-product of clay, as a building material. (The Granger Collection, New York) fine and consist primarily of various forms of hydrous aluminum silicates along with organic material and other minerals. Bricks are usually shaped in a mold and then left in the sun to dry. Dried bricks may then be placed in a kiln for a process called “burning,” in which they are heated enough to cause the clay parti- cles to fuse. The ancient city of Babylon, which reached its zenith under Nebuchadnezzar in the sixth century b.c.e., was built with bricks. Its massive outer wall was built with a core of sun-dried brick and faced with burned brick. The famous Ishtar gate stood 12 meters high and featured 575 glazed brick mosaics in which golden dragons and young bulls stood out in relief against a blue-green background. One hundred twenty golden lions on blue-green backgrounds lined the walls of the street that led from the Ishtar gate to the temple of Marduk. Pottery and Porcelain Pottery making is probably as old as civilization itself. To be durable, aclay pot must be fired ina kiln so that clay particles fuse and the glaze (if present) melts to form a glassy surface. In the Near East, pottery dating back to the seventh millennium b.c.e. has been dis- covered. Painted pottery was already common in northern Mesopotamia before 5000 b.c.e., and the high-speed potter’s wheel was used in ancient Susa by 4000 b.c.e. About that same time, the Egyptians be- gan working with colorful and lustrous glazes that may have led them to the development of glass. Porcelain is a type of ceramic made from kaolin (a special white clay with very few impurities), feldspar (aluminum silicates), and quartz (silica). Porcelain paste is stiff and harder to shape than normal clay paste, but it retains its shape well at high tempera- tures. Because of this, porcelain pieces with very thin walls can be made. The Chinese became experts at crafting porcelain pieces and in using colorful enam- els and glazes to decorate them. Vases made during the Ming dynasty (1368-1644 c.e.) have become leg- endary. Glass Some of the oldest glass objects known are beads found inan Egyptian tombdated at 2500 b.c.e. About a thousand years later, the first glass vessels appear in Egypt. These vessels were made by winding a string of glass around a claymold held on the endof a rod. The technique of glassblowing was in use by the first cen - tury b.c.e., although some tomb murals indicate it may have been used much earlier. The Romans were the first to use glass windows, and there are glass windows in the public baths of Pompeii, the city destroyed by an eruption of Mount Vesuvius in 79 c.e. As they did with pottery, some art- ists created glass vessels ofexquisite beauty. Otherart- ists turned their talents to stained-glass windows such as those of the Sainte-Chapelle in Paris (consecrated in 1248 c.e.). Itsstained-glasswindowsdepicting bibli- cal scenes completely dominate the walls and soar upward in a kaleidoscope of red, blue, green, yellow, and white. The chief constituent of glass is white sand (silica), but melting pure silica requires a temperature above 1,700° Celsius. If soda ash (sodium carbonate) is added as a flux, the melting point is reduced to 850° Celsius, a temperature more easily achieved. The re- sulting glass is water soluble, but adding limestone (calcium carbonate) to the melt results in insoluble glass. A typical mixture is 75 percent silica, 10 percent lime, and 15 percent soda. Soda ash can be obtained by leaching wood or seaweedashorbymining natron, another salt deposited as an entrapped sea evapo- rates. The Seven Metals of Antiquity As far back as 8000 b.c.e., Stone Age people gathered shining bits of gold to use as ornaments and decora- tions. Seams of gold in solid rock such as granite are called lode deposits. They are mined by tunneling into the rock. As gold-bearing rock weathers away, gold dust and gold nuggets wash into streambeds to form placer deposits.Placer deposits may bemined by scooping up sand and gravel in a pan and then care- fully washing away everything but the dense grains of gold. The storyof Jason and theGoldenFleece proba- bly refers to the ancient practice of placing a fleece in running water where it could collect gold dust as placer deposit sand was washed over it. The golden death maskof Tutankhamen (1352 b.c.e.) is an excel- lent example of the artistry with which gold was worked in ancient times. Copper was discovered about the same time as gold, since it can also be found naturally as a metal. Copper pinsdating from 7000b.c.e. have been found in Turkey. Malachite is a green-colored copper ore of- ten foundnear a seam of coppermetal. Copper metal may be produced from malachite by mixing it with charcoal and heating the mixture in a kiln. The earli - 754 • Mineral resource use, early history of Global Resources est tools cast from molten copper appear in Mesopo - tamia around 4000 b.c.e. Lead may have been the next metal discovered, since leadbeads dated to6500 b.c.e. have been found in Turkey. Lead does not occur as a free metal in na- ture, but the lead ore called galena (lead sulfide)does have a metallic look. If galena is combined with char- coal and heated to only 327° Celsius, metallic lead is produced. Since lead is soft and ductile, the Romans found it well suited for making pipes. Lead often con- tains traces of silver. Silver artifacts date back to about 4000 b.c.e. Metallic silver is rarely found in nature, but it does occur. Pure silver is harder than gold but softer than copper.As with gold, silverwasfirst used to make ornaments and jewelry. By 2500 b.c.e. the Sumerians discovered that mix- ing different types of ore produced ametal that melted at a lower temperature and was harder than copper. They had produced a copper-tin alloy now called bronze. Bronze was widely used to make tools and weapons. Tin was not produced as a separate metal until five hundred yearslater. Tin ore isstannic oxide, a hard material that remains after softer surrounding rock weathersaway. Mercury can be obtained by heat- ing cinnabar (mercury sulfide) in the presence of oxy- gen. Mercury has been found in tombs dating from 1500 b.c.e. It is a liquid at room temperature and can dissolve silver andgold to form an amalgam, aprocess that is sometimes used in mining. Smelted iron did not become common until around 1500 b.c.e., although it was first produced one thousand years earlier; meteoric iron was used even before that. Metallic iron may beproduced by heating a mixture of hematite (iron oxide) and charcoal in a kiln. Only the rich couldafford bronze, but when iron became cheaperthan bronze, iron tools and weapons were made in large numbers. Being more broadly dis- tributed through society than bronze, iron greatly changed farming and warfare. Salt Salt (sodium chloride) is essential for human health. It isgenerally accepted that a diet consisting mostly of raw or roasted meat requires no added salt, but if the meat is boiled or if the diet consists primarily of grains, somesalt is essential.Salt has also been usedas a preservative for fish and meat since ancient times. People collected salt atbrine springsor from dried tidal pools at the seashore. Later, ocean water was let into artificial pools that were then sealed and allowed to dry. In colder climatessaltwaterwas boiled down in ceramic trays and later in metal trays. Many areas of the world have underground salt beds formed as an- cient seas dried up. Rock salt has been mined from such deposits beginning in Roman times, if not ear- lier. Petroleum Products and Natural Gas The use of petroleum goes back to the Stone Age, when bitumen was used to cement stones to wooden handles. (“Bitumen,” loosely used, refers to various tars and asphalt.) The Sumerians, in 3000 b.c.e., and later the Assyrians and the Babylonians, used a mortar of bitumen, sand, and reeds for their great brick structures. They also made asphalt roads, used tar as an adhesive for tiles, and caulked ships with tar. Dioscorides, a surgeon in Nero’s army, said that the Sicilians burned petroleum oil in their lamps in place of olive oil. Eventually, petroleum grease was used as a lubricant, paraffin wax was used for candles, and naphtha (a highly volatile oil) found use as an incen- diary agent in warfare. At first, bitumen wastakenfromnaturaltarpitsand oil and gas seeps. Three ofthe most famousare theLa Brea TarPits of California,thePitch Lake of Trinidad, and the Perpetual Fires of Baku, a large gas seep area in Azerbaijan. Later, oil was taken from tunnels and pits dug near oil seeps. By the sixthcentury b.c.e., the Chinese could drillwells 100 meters deep.Whiledrill- ing for fresh water or salt water, Chinese miners occa- sionally found oil or natural gas instead. This is exactly what happened to the Chinese while drilling for salt water in Sichuan about 250 c.e. Being opportunists, the workers at some salt works burned the gas to pro- vide heat to evaporate the brine. With the passage of time, the production anduse of petroleum increased, but it didnot become amajorresource until kerosene became cheaper thanwhaleoil in the mid-nineteenth century. Coal Coal is the fossilized remains of plants that lived hun- dreds of millions of years ago. A coal bed begins as a thick layer of peat in a swamp that is later invaded by the advancing sea. Layers of sediment compress the peat, which dries, hardens, and eventually turns into coal. Coal consists primarily of carbon but also con- tains smaller amounts of water, light oil, tar, sulfur, and phosphorus. The Chinese are said to have used coal in the first Global Resources Mineral resource use, early history of • 755 century b.c.e., and in the thirteenth century c.e. Marco Polo described a black stone that the Chinese dug from the mountains and burned for fuel. Polo seems to have been unaware that coal was already used in Europe and England. In fact, Theophrastus described various Mediterranean locations where coal was used as fuel in the fourth century b.c.e. Long be- fore Polo’s time, “sea coal” was gathered regularly from some of England’s beaches, where it washed ashore, and coal was mined from shallow pits in other regions. However, Europeans used coal only on a small scale until the fifteenth century c.e., when it became widely used in kilns. Charles W. Rogers Further Reading Agricola, Georgius. De re metallica: Translated from the First Latin Edition of 1556 with Biographical Introduc- tion, Annotations andAppendicesupon the Development of Mining Methods, Metallurgical Processes, Geology, Mineralogy and Mining Law from the Earliest Times to the Sixteenth Century by Herbert Clark Hoover and Lou Henry Hoover. Reprint. New York: Dover, 1986. Buranelli, Vincent. Gold: An Illustrated History. Maple- wood, N.J.: Hammond, 1979. Camusso, Lorenzo, and Sandro Bortone, eds. Ceramics of the World: From 4000 B.C. to the Present. New York: H. N. Abrams, 1991. Craddock, Paul, and JanetLang.Miningand Metal Pro- duction Through the Ages. London: British Museum, 2003. Freese, Barbara. Coal: A Human History. Cambridge, Mass.: Perseus, 2003. Hawkes, Jacquetta. The Atlas of Early Man. 1976. Re- print. New York: St. Martin’s Press, 1993. Lynch, Martin.MininginWorld History. London: Reak- tion, 2002. Macfarlane, Alan, and Gerry Martin. Glass: A World History. Chicago: University of Chicago Press,2002. Multhauf, RobertP. Neptune’s Gift: AHistory of Common Salt. Baltimore: Johns Hopkins University Press, 1978. Wertime, Theodore A., and James D. Muhly, eds. The Coming of the Age of Iron. New Haven, Conn.: Yale University Press, 1980. See also: Brick; Bronze; Ceramics; Clays; Coal; Cop- per; Glass; Gold; Iron; Lead; Mercury; Metals and metallurgy; Native elements; Oil and natural gas drill - ing and wells; Silver; Tin; Zinc. Minerals, structure and physical properties of Category: Mineral and other nonliving resources Minerals—naturally occurring inorganic solids with definite chemical composition and definite crystal structure—are the primary constituents of rocks; they are also found in soil. The variety of minerals is huge, and their myriad applications range from use as gem- stones and precious metals to applications in building materials, electronics, food, and pharmaceuticals. Background Minerals are the building blocks of rocks, and they have many economic uses. Mineralssuch as diamond, ruby, emerald, and sapphireareprecious gems. Other minerals are valuable metals (gold, silver, platinum, copper) or metal ores, such as hematite (iron), sphalerite (zinc), galena (lead), and bauxite (alumi- num). Other minerals are used as salt (halite), lubri- cants (graphite), abrasives (corundum), and fertil- izer (apatite), as well as in pharmaceuticals (sulfur), steel making (fluorite), plaster (gypsum and anhy- drite), lime, and portland cement (calcite and dolo- mite). A mineral is defined as a naturally occurring, inor- ganic solid with a definite chemical composition (or range of compositions within certain limits) that can be expressed by a chemical formula, and an orderly internal crystalline structure (its atoms are arranged in a definite pattern which is reflected in the shape of its crystals and in its cleavage). Only substances that meet these precise requirements are considered min- erals. As a result, synthetic gems, which may be physi- cally and chemically identical to natural gemstones, are not considered minerals. Minerals have specific physical properties that re- sult from their chemical composition and crystal structure, and many minerals can be identified by these properties. Physical properties include hard- ness, color, luster, streak, cleavage, density or specific gravity, and crystal form. Some minerals also have additional diagnostic physical properties, including tenacity, taste, magnetism, electrical properties, lumi - nescence, reaction to hydrochloric acid, and radio - activity. 756 • Minerals, structure and physical properties of Global Resources Hardness Hardness is a mineral’s resistance to scratching or abrasion and is a result of crystal structure or atomic arrangement. The stronger the chemical bonds be- tween the atoms, the harder the mineral. For exam- ple, two minerals may have an identical chemical composition but different crystal structures, such as diamond and graphite, which are both carbon. Dia - mond is thehardest known mineral,but graphite isso soft that it rubs off on the fingers or a piece of paper (it is used as pencil “lead”). The differences in crystal structure produce the vastly different hardnesses of these two minerals. Ten minerals have been arranged in order of in- creasing hardness and are referred to as the Mohs hardness scale, devised in 1822 by a German mineral- ogist, Friedrich Mohs. The minerals of the Mohs hard- ness scale, in order from softest to hardest, are: (1) talc, (2) gypsum, (3) calcite, (4) fluorite, (5) apatite, (6) potassium feldspar (orthoclase), (7) quartz, (8) Global Resources Minerals, structure and physical properties of • 757 Physical Properties of Minerals Property Explanation Chemical composition Chemical formula that defines the mineral Cleavage Tendency to break in smooth, flat planes along zones of weak bonding; depends on structure Color Depends on presence of major elements in the chemical composition; may be altered by trace elements or defects in structure; often not definitive Crystal shape Outward expression of the atomic crystal structure Crystal structure Three-dimensional ordering of the atoms that form the mineral Density Mass per unit volume (grams per cubic centimeter) Electrical properties Properties having to do with electric charge; quartz, for example, is piezoelectric (emits charge when squeezed) Fracture Tendency for irregular breakage (not along zones of weak bonding) Hardness Resistance of mineral to scratching or abrasion; measured on a scale of 1-10 (Mohs hardness scale) Luminescence Emission of electromagnetic waves from mineral; some minerals are fluorescent, some thermoluminescent Luster Reflectivity of the surface; may be either metallic or nonmetallic Magnetism Degree to which mineral is attracted to a magnet Radioactivity Instability of mineral; radioactive minerals are always isotopes Specific gravity Relative density: ratio of weight of substance to weight of equal volume of water at 4° Celsius Streak Color of powdered form; more definitive than color Taste Salty, bitter, etc.; applies only to some minerals Tenacity Resistance to bending, breakage, crushing, tearing: termed as brittle, malleable, ductile, sectile, flexible, or elastic . Bureau of Land Management in the U.S. Department of the In- terior, often demand larger than average bonuses be- cause they may control the fate of mineral develop- ment. The most important part of. value calculations. Determination of Ownership The determination of mineral ownership is similar to determination of surface ownership. Title searches are made by professionals who execute a study of the ownership history of. particles are very Global Resources Mineral resource use, early history of • 753 The Sumerian temple of Ur, in present-day Iraq, is an early example of the use of brick, a by-product of clay, as a building