2 9.2 Economic Minerals
Mining is the extraction from the Earth of valuable material for societal use. Usually, this includes solid materials (e.g. gold, iron,
coal, diamond, sand, and gravel), but can also include fluid resources such as oil.
Mining has a long relationship with modern society. The oldest evidence of concentrated area of digging into the Earth for materials has a history that may go back 40,000 years to the hematite (used as a red dye) of the Lion Cave in Swaziland [1].
Mineral resources, like other natural resources, are unevenly distributed on Earth. This is not random, geological processes mandate the distribution of mineral resources. For example, notice in Fig 9.6 how copper deposits (yellow triangles) are found along the western margin of the Americas, while iron deposits (red triangles) are concentrated mostly on the Midwest of the United States. The cause of the heterogeneous distribution relates to the different geologic histories of these areas.
Human populations have historically concentrated at sites that are geologically advantageous to commerce, food production, and other aspects of civilization. Indeed, Geology has shaped human history! The uneven distribution has extremely important social, economic, and political implications. The opposite is true, policy, economics, and other factors result in uneven production; few countries control mineral production. This means that countries depend on other countries for resources. Although this seems like a problem, it is evidence of our interconnectedness and interdependence, and, ideally; it encourages governments to collaborate and maintain peace with each other. Observe in Figure 9.7 which countries supply the most material to the US.
Classification of Mineral Resources
We can classify mineral resources in various ways, according to their use (industrial, agricultural, construction), their relative abundance (scarce, rare, abundant), or their perceived value (precious vs. base metals), etc. A practical classification is to divide them into non-fuel and fuel minerals. Nonfuel minerals can be further be divided into Metals and metallic resources, natural aggregates, and other industrial minerals, as shown in Table 2. We will study the general mining aspects of nonfuel minerals. Chapter 10 will address fuel minerals.
| Ch. 9. Nonfuel Minerals | Metal or Metallic | aluminum, iron, copper, lead, zinc, tin, gold, silver, etc. |
| Natural Aggregates | cement, sand, gravel, and crushed stone | |
| Other Industrial Minerals | Borates, salt, lime, phosphate rock, soda ash, clay minerals, gypsum, industrial sand, iron oxide pigments, Iodine, Magnesium compounds, mica, peat, perlite, pumice, talk. | |
| Ch. 10. Energy Fuel Minerals | Hydrocarbons | Petroleum, natural gas, coal, unconventional hydrocarbons |
| Non Hydrocarbons | Uranium |
Table 2. Classification of Mineral Commodities. Source: Michel, C.L
Metal Mining
The periodic table contains the known elements that make up the Earth. However, it is rare for the amount of the element to be concentrated to the point where the extraction and processing of the material become profitable. Mineral deposits in which the material can be mined at a profit are called ore deposits. Geologists evaluate the size of the deposit, the concentration of the ore mineral(s), and the production and transportation costs to determine if a deposit is economical. Typically, the term ore is used for only metal-bearing minerals, though the concept of ore as a non-renewable resource can be applied to valuable concentrations of fossil fuels, building stones, and other non-metal deposits, even groundwater. The term “natural resource” is more common than ore for these types of materials [1].
It is implicit that the technology to mine is available, economic conditions are suitable, and political, social, and environmental considerations are satisfied in order to classify a natural resource deposit as ore. Depending on the substance, it can be concentrated in a narrow vein or distributed over a large area as a low-concentration ore. Some materials are mined directly from bodies of water (e.g. sylvite for potassium; water through desalination) and the atmosphere (e.g. nitrogen for fertilizers). These differences lead to various methods of mining, and differences in terminology depending on the certainty. Ore mineral resource is used for an indication of ore that is potentially extractable, and the term ore mineral reserve is used for a well-defined (proven), profitable amount of extractable ore [1].
Common Ore Minerals
Ore minerals contain elements and compounds concentrated by factors of hundreds, thousands, or tens of thousands as compared with their average concentrations within the Earth’s crust. For example, the average crustal abundance for gold is 0.0000002%. A gold accumulation should have 4,000-5,000 times the crustal concentration to be profitable. Figure 9.8 shows one of the copper ore minerals, Bornite. We use copper for electrical wires, plumbing, and electronics. Table 3 presents other ore minerals. Refer to Chapter 3 if you need a refresher on mineral properties.
| MINERAL | STREAK | LUSTER | HARDNESS | OTHER PHYSICAL | ORE FOR |
 |
White | Vitreous (Glassy) | 9 | Forms hexagonal prisms. | Aluminum, used in the automotive industry and to create alloys. The cosmetic industry uses aluminum in salts |
 |
Dark gray | Metallic | 6.5 | Color can vary between red, black but streak color is red | Iron, the main ingredient in steel |
|
Bright red | Adamantine | 2-2.5 – Gypsum-Finger Nail | It can have a Lead gray, Brown, Brown pink, Vermilion, Gray color. | Mercury. Used in thermometers, barometers, to separate gold and in vapor/gas form for fluorescent and neon lights |
definition
Valuable material in the Earth, typically used for metallic mineral resources.
