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Natural resource economics deals with the supply,
demand In economics, demand is the quantity of a good that consumers are willing and able to purchase at various prices during a given time. The relationship between price and quantity demand is also called the demand curve. Demand for a specific item ...
, and allocation of the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surf ...
's
natural resource Natural resources are resources that are drawn from nature and used with few modifications. This includes the sources of valued characteristics such as commercial and industrial use, aesthetic value, scientific interest and cultural value. ...
s. One main objective of natural resource economics is to better understand the role of natural resources in the economy in order to develop more
sustainable Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livin ...
methods of managing those resources to ensure their availability for future generations. Resource economists study interactions between economic and natural systems, with the goal of developing a sustainable and efficient economy.


Areas of discussion

Natural resource economics transdisciplinary field of academic research within
economics Economics () is the social science that studies the production, distribution, and consumption of goods and services. Economics focuses on the behaviour and interactions of economic agents and how economies work. Microeconomics analy ...
that aims to address the connections and interdependence between human economies and natural
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
s. Its focus is how to operate an
economy An economy is an area of the production, distribution and trade, as well as consumption of goods and services. In general, it is defined as a social domain that emphasize the practices, discourses, and material expressions associated with t ...
within the ecological constraints of earth's
natural resources Natural resources are resources that are drawn from nature and used with few modifications. This includes the sources of valued characteristics such as commercial and industrial use, aesthetic value, scientific interest and cultural value. ...
.Encyclopedia of Earth
Article Topic: ecological economics
/ref> Resource economics brings together and connects different disciplines within the natural and social sciences connected to broad areas of
earth science Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spher ...
, human economics, and natural ecosystems. Economic models must be adapted to accommodate the special features of natural resource inputs. The traditional curriculum of natural resource economics emphasized fisheries models, forestry models, and minerals extraction models (i.e. fish, trees, and ore). In recent years, however, other resources, notably air, water, the global climate, and "environmental resources" in general have become increasingly important to policy-making. Academic and policy interest has now moved beyond simply the optimal commercial exploitation of the standard trio of resources to encompass management for other objectives. For example, natural resources more broadly have defined recreational, as well as commercial values. They may also contribute to overall social welfare levels, by their mere existence. The economics and policy area focuses on the human aspects of environmental problems. Traditional areas of environmental and natural resource economics include welfare theory, land/location use, pollution control, resource extraction, and non-market valuation, and also resource exhaustibility,
sustainability Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livin ...
,
environmental management Environmental resource management is the management of the interaction and impact of human societies on the environment. It is not, as the phrase might suggest, the management of the environment itself. Environmental resources management aims ...
, and
environmental policy Environmental policy is the commitment of an organization or government to the laws, regulations, and other policy mechanisms concerning environmental issues. These issues generally include air and water pollution, waste management, ecosystem ...
. Research topics could include the environmental impacts of agriculture, transportation and urbanization, land use in poor and industrialized countries, international trade and the environment,
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
, and methodological advances in non-market valuation, to name just a few. Hotelling's rule is a 1938 economic model of non-renewable
resource management In organizational studies, resource management is the efficient and effective development of an organization's resources when they are needed. Such resources may include the financial resources, inventory, human skills, production resources, or i ...
by Harold Hotelling. It shows that efficient exploitation of a nonrenewable and nonaugmentable resource would, under otherwise stable economic conditions, lead to a depletion of the resource. The rule states that this would lead to a net price or "Hotelling rent" for it that rose annually at a rate equal to the rate of interest, reflecting the increasing scarcity of the resource. Nonaugmentable resources of inorganic materials (i.e. minerals) are uncommon; most resources can be augmented by recycling and by the existence and use of substitutes for the end-use products (see below). Vogely has stated that the development of a mineral resource occurs in five stages: (1) The current operating margin (rate of production) governed by the proportion of the reserve (resource) already depleted. (2) The intensive development margin governed by the trade-off between the rising necessary investment and quicker realization of revenue. (3) The extensive development margin in which extraction is begun of known but previously uneconomic deposits. (4) The exploration margin in which the search for new deposits (resources) is conducted and the cost per unit extracted is highly uncertain with the cost of failure having to be balanced against finding usable resources (deposits) that have marginal costs of extraction no higher than in the first three stages above. (5) The technology margin which interacts with the first four stages. The Gray-Hotelling (exhaustion) theory is a special case, since it covers only Stages 1–3 and not the far more important Stages 4 and 5. Simon has stated that the supply of natural resources is infinite (i.e. perpetual) These conflicting views will be substantially reconciled by considering resource-related topics in depth in the next section, or at least minimized. Furthermore, Hartwick's rule provides insight to the sustainability of welfare in an economy that uses
non-renewable resource A non-renewable resource (also called a finite resource) is a natural resource that cannot be readily replaced by natural means at a pace quick enough to keep up with consumption. An example is carbon-based fossil fuels. The original organic mat ...
s.


Perpetual resources vs. exhaustibility


Background and introduction

The perpetual resource concept is a complex one because the concept of resource is complex and changes with the advent of new technology (usually more efficient recovery), new needs, and to a lesser degree with new economics (e.g. changes in prices of the material, changes in energy costs, etc.). On the one hand, a material (and its resources) can enter a time of shortage and become a strategic and critical material (an immediate exhaustibility crisis), but on the other hand a material can go out of use, its resource can proceed to being perpetual if it was not before, and then the resource can become a paleoresource when the material goes almost completely out of use (e.g. resources of arrowhead-grade flint). Some of the complexities influencing resources of a material include the extent of recyclability, the availability of suitable substitutes for the material in its end-use products, plus some other less important factors. The Federal Government suddenly became compellingly interested in resource issues on December 7, 1941, shortly after which Japan cut the U.S. off from tin and
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, a ...
and made some other materials, such as tungsten, very difficult to obtain. This was the worst case for resource availability, becoming a strategic and critical material. After the war a government stockpile of strategic and critical materials was set up, having around 100 different materials that were purchased for cash or obtained by trading off U.S. agricultural commodities for them. In the longer term, scarcity of tin later led to completely substituting
aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It h ...
foil for tin foil and polymer lined steel cans and
aseptic Asepsis is the state of being free from disease-causing micro-organisms (such as pathogenic bacteria, viruses, pathogenic fungi, and parasites). There are two categories of asepsis: medical and surgical. The modern day notion of asepsis is deriv ...
packaging substituting for tin electroplated steel cans. Resources change over time with technology and economics; more efficient recovery leads to a drop in the ore grade needed. The average grade of the
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
ore processed has dropped from 4.0% copper in 1900 to 1.63% in 1920, 1.20% in 1940, 0.73% in 1960, 0.47% in 1980, and 0.44% in 2000.
Cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, ...
had been in an iffy supply status ever since the
Belgian Congo The Belgian Congo (french: Congo belge, ; nl, Belgisch-Congo) was a Belgian colony in Central Africa from 1908 until independence in 1960. The former colony adopted its present name, the Democratic Republic of the Congo (DRC), in 1964. Colo ...
(world's only significant source of cobalt) was given a hasty independence in 1960 and the cobalt-producing province seceded as Katanga, followed by several wars and insurgencies, local government removals, railroads destroyed, and nationalizations. This was topped off by an invasion of the province by Katangan rebels in 1978 that disrupted supply and transportation and caused the cobalt price to briefly triple. While the cobalt supply was disrupted and the price shot up, nickel and other substitutes were pressed into service. Following this, the idea of a "Resource War" by the Soviets became popular. Rather than the chaos that resulted from the Zairean cobalt situation, this would be planned, a strategy designed to destroy economic activity outside the Soviet bloc by the acquisition of vital resources by noneconomic means (military?) outside the Soviet bloc (Third World?), then withholding these minerals from the West. An important way of getting around a
cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, ...
situation or a "Resource War" situation is to use substitutes for a material in its end-uses. Some criteria for a satisfactory substitute are (1) ready availability domestically in adequate quantities or availability from contiguous nations, or possibly from overseas allies, (2) possessing physical and chemical properties, performance, and longevity comparable to the material of first choice, (3) well-established and known behavior and properties particularly as a component in exotic alloys, and (4) an ability for processing and fabrication with minimal changes in existing technology, capital plant, and processing and fabricating facilities. Some suggested substitutions were
alunite Alunite is a hydroxylated aluminium potassium sulfate mineral, formula K Al3( S O4)2(O H)6. It was first observed in the 15th century at Tolfa, near Rome, where it was mined for the manufacture of alum. First called ''aluminilite'' by J.C. De ...
for bauxite to make alumina,
molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with le ...
and/or
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
for cobalt, and aluminum alloy automobile radiators for copper alloy automobile radiators. Materials can be eliminated without material substitutes, for example by using discharges of high tension electricity to shape hard objects that were formerly shaped by mineral abrasives, giving superior performance at lower cost,Charles W. Merrill "Mineral Obsolescence and Substitution" "Mining Engineering", AIME, Society of Mining Engineers, September 1964, pp. 55-59 or by using computers/satellites to replace copper wire (land lines). An important way of replacing a resource is by synthesis, for example, industrial
diamonds Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...
and many kinds of
graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
, although a certain kind of graphite could be almost replaced by a recycled product. Most graphite is synthetic, for example, graphite electrodes, graphite fiber, graphite shapes (machined or unmachined), and graphite powder. Another way of replacing or extending a resource is by recycling the material desired from scrap or waste. This depends on whether or not the material is dissipated or is available as a no longer usable durable product. Reclamation of the durable product depends on its resistance to chemical and physical breakdown, quantities available, price of availability, and the ease of extraction from the original product. For example,
bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
in stomach medicine is hopelessly scattered (dissipated) and therefore impossible to recover, while bismuth alloys can be easily recovered and recycled. A good example where recycling makes a big difference is the resource availability situation for graphite, where flake graphite can be recovered from a renewable resource called kish, a steelmaking waste created when carbon separates out as graphite within the kish from the molten metal along with slag. After it is cold, the kish can be processed. Several other kinds of resources need to be introduced. If strategic and critical materials are the worst case for resources, unless mitigated by substitution and/or recycling, one of the best is an abundant resource. An abundant resource is one whose material has so far found little use, such as using high-aluminous clays or anorthosite to produce alumina, and magnesium before it was recovered from seawater. An abundant resource is quite similar to a perpetual resource. The reserve base is the part of an identified resource that has a reasonable potential for becoming economically available at a time beyond when currently proven technology and current economics are in operation. Identified resources are those whose location, grade, quality, and quantity are known or estimated from specific geologic evidence. Reserves are that part of the reserve base that can be economically extracted at the time of determination; reserves should not be used as a surrogate for resources because they are often distorted by taxation or the owning firm's public relations needs.


Comprehensive natural resource models

Harrison Brown and associates stated that humanity will process lower and lower grade "ore". Iron will come from low-grade iron-bearing material such as raw rock from anywhere in an
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
formation, not much different from the input used to make
taconite Taconite () is a variety of iron formation, an iron-bearing (over 15% iron) sedimentary rock, in which the iron minerals are interlayered with quartz, chert, or carbonate. The name "taconyte" was coined by Horace Vaughn Winchell (1865–1923) � ...
pellets in North America and elsewhere today. As coking coal reserves decline, pig iron and steel production will use non-coke-using processes (i.e. electric steel). The
aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It h ...
industry could shift from using
bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(O ...
to using anorthosite and
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay part ...
.
Magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
metal and magnesia consumption (i.e. in refractories), currently obtained from seawater, will increase. Sulfur will be obtained from pyrites, then
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and dr ...
or anhydrite. Metals such as
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
,
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic t ...
,
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
, and
lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
will be obtained from manganese nodules or the Phosphoria formation (sic!). These changes could occur irregularly in different parts of the world. While Europe and North America might use anorthosite or clay as raw material for aluminum, other parts of the world might use bauxite, and while North America might use taconite, Brazil might use iron ore. New materials will appear (note: they have), the result of technological advances, some acting as substitutes and some with new properties. Recycling will become more common and more efficient (note: it has!). Ultimately, minerals and metals will be obtained by processing "average" rock. Rock, 100 tonnes of "average" igneous rock, will yield eight tonnes of aluminum, five tonnes of iron, and 0.6 tonnes of titanium. The USGS model based on crustal abundance data and the reserve-abundance relationship of McKelvey, is applied to several metals in the Earth's crust (worldwide) and in the U.S. crust. The potential currently recoverable (present technology, economy) resources that come closest to the McKelvey relationship are those that have been sought for the longest time, such as copper, zinc, lead,
silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
,
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
and
molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with le ...
. Metals that do not follow the McKelvey relationship are ones that are byproducts (of major metals) or have not been vital to the economy until recently (
titanium Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...
, aluminum to a lesser degree). Bismuth is an example of a byproduct metal that does not follow the relationship very well; the 3% lead reserves in the western U.S. would have only 100 ppm bismuth, clearly too low-grade for a bismuth reserve. The world recoverable resource potential is 2,120 million tonnes for copper, 2,590 million tonnes for nickel, 3,400 million tonnes for zinc, 3,519 billion tonnes for aluminum, and 2,035 billion tonnes for iron. Diverse authors have further contributions. Some think the number of substitutes is almost infinite, particularly with the flow of new materials from the chemical industry; identical end products can be made from different materials and starting points. Plastics can be good electrical conductors. Since all materials are 100 times weaker than they theoretically should be, it ought to be possible to eliminate areas of dislocations and greatly strengthen them, enabling lesser quantities to be used. To summarize, "mining" companies will have more and more diverse products, the world economy is moving away from materials towards services, and the population seems to be levelling, all of which implies a lessening of demand growth for materials; much of the materials will be recovered from somewhat uncommon rocks, there will be much more coproducts and byproducts from a given operation, and more trade in minerals and materials.


Trend towards perpetual resources

As radical new technology impacts the materials and minerals world more and more powerfully, the materials used are more and more likely to have perpetual resources. There are already more and more materials that have perpetual resources and less and less materials that have nonrenewable resources or are strategic and critical materials. Some materials that have perpetual resources such as
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quanti ...
, stone,
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
, and common clay were mentioned previously. Thanks to new technology, synthetic
diamonds Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...
were added to the list of perpetual resources, since they can be easily made from a lump of another form of carbon. Synthetic graphite, is made in large quantities (graphite electrodes, graphite fiber) from carbon precursors such as petroleum coke or a textile fiber. A firm named Liquidmetal Technologies, Inc. is utilizing the removal of dislocations in a material with a technique that overcomes performance limitations caused by inherent weaknesses in the crystal atomic structure. It makes amorphous metal
alloys An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
, which retain a random atomic structure when the hot metal solidifies, rather than the crystalline atomic structure (with dislocations) that normally forms when hot metal solidifies. These amorphous alloys have much better performance properties than usual; for example, their zirconium-titanium Liquidmetal alloys are 250% stronger than a standard titanium alloy. The Liquidmetal alloys can supplant many high performance alloys. Exploration of the ocean bottom in the last fifty years revealed manganese nodules and phosphate nodules in many locations. More recently, polymetallic sulfide deposits have been discovered and polymetallic sulfide "black muds" are being presently deposited from "black smokers" The cobalt scarcity situation of 1978 has a new option now: recover it from manganese nodules. A Korean firm plans to start developing a
manganese nodule Polymetallic nodules, also called manganese nodules, are mineral concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. As nodules can be found in vast quantities, and contain valuable metals, ...
recovery operation in 2010; the manganese nodules recovered would average 27% to 30%
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy u ...
, 1.25% to 1.5% nickel, 1% to 1.4% copper, and 0.2% to 0.25% cobalt (commercial grade) Nautilus Minerals Ltd. is planning to recover commercial grade material averaging 29.9% zinc, 2.3% lead, and 0.5% copper from massive ocean-bottom polymetallic sulfide deposits using an underwater vacuum cleaner-like device that combines some current technologies in a new way. Partnering with Nautilus are Tech Cominco Ltd. and Anglo-American Ltd., world-leading international firms. There are also other robot mining techniques that could be applied under the ocean. Rio Tinto is using satellite links to allow workers 1500 kilometers away to operate drilling rigs, load cargo, dig out ore and dump it on conveyor belts, and place explosives to subsequently blast rock and earth. The firm can keep workers out of danger this way, and also use fewer workers. Such technology reduces costs and offsets declines in metal content of ore reserves. Thus a variety of minerals and metals are obtainable from unconventional sources with resources available in huge quantities. Finally, what is a perpetual resource? The ASTM definition for a perpetual resource is "one that is virtually inexhaustible on a human time-scale". Examples given include solar energy, tidal energy, and wind energy, to which should be added salt, stone, magnesium, diamonds, and other materials mentioned above. A study on the biogeophysical aspects of sustainability came up with a rule of prudent practice that a resource stock should last 700 years to achieve sustainability or become a perpetual resource, or for a worse case, 350 years. If a resource lasting 700 or more years is perpetual, one that lasts 350 to 700 years can be called an abundant resource, and is so defined here. How long the material can be recovered from its resource depends on human need and changes in technology from extraction through the life cycle of the product to final disposal, plus recyclability of the material and availability of satisfactory substitutes. Specifically, this shows that exhaustibility does not occur until these factors weaken and play out: the availability of substitutes, the extent of recycling and its feasibility, more efficient manufacturing of the final consumer product, more durable and longer-lasting consumer products, and even a number of other factors. The most recent resource information and guidance on the kinds of resources that must be considered is covered on the Resource Guide-Updat


Transitioning: perpetual resources to paleoresources

Perpetual resources can transition to being a paleoresource. A paleoresource is one that has little or no demand for the material extracted from it; an obsolescent material, humans no longer need it. The classic paleoresource is an arrowhead-grade
flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and sta ...
resource; no one makes flint arrowheads or spearheads anymore—making a sharpened piece of scrap steel and using it is much simpler. Obsolescent products include tin cans, tin foil, the schoolhouse
slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic ro ...
blackboard, and
radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rathe ...
in medical technology. Radium has been replaced by much cheaper
cobalt-60 Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2713 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisot ...
and other radioisotopes in radiation treatment. Noncorroding lead as a cable covering has been replaced by plastics. Pennsylvania
anthracite Anthracite, also known as hard coal, and black coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the hig ...
is another material where the trend towards obsolescence and becoming a paleoresource can be shown statistically. Production of anthracite was 70.4 million tonnes in 1905, 49.8 million tonnes in 1945, 13.5 million tonnes in 1965, 4.3 million tonnes in 1985, and 1.5 million tonnes in 2005. The amount used per person was 84 kg per person in