Mining

V

Ocean Metal Mining

In addition to the conventional methods of mining metallic ores where they occur on land, methods of deep-sea mining were devised in the 1970s using modern technology to collect manganese nodules—concretions cemented by iron oxide and rich in copper, cobalt, manganese, and nickel—from areas, primarily in the Pacific Ocean, where they lie scattered on the deep-sea floor. The feasibility of the process has been demonstrated by prototype operations in which bargelike surface craft serve as a base for dragline, dragnet, or suction-hose collectors. That deep-sea mining has yet to begin on a commercial basis is due to economics as well as politics. Besides being an inherently costly process with dubious profit potential under present market conditions, the issue of deep-sea mining has forced the nations of the world to consider the question of the ownership of the mineral wealth of the deep-sea bed. The United Nations Convention on the Law of the Sea, adopted in 1982 over U.S. opposition and not yet in force, holds that coastal states must share with the international community the revenue they derive from deep-sea mining outside their territorial waters.

VI

Nonmetalliferous Mineral Mining

Industrial minerals and rocks, from which no metal is extracted, are usually mined by the methods already described. Because these deposits tend to be of large bulk and low unit value, low-cost mining methods are most common, and surface-mining methods are used wherever possible. Room-and-pillar mining is a popular underground method for bedded deposits of potash, trona, rock salt, and talc, and block-caving is used for the massive asbestos deposits. The relative economic importance of the nonmetals, coal, and metals may be illustrated by the statistics of production in the United States. At the beginning of the 21st century, the value of all nonfuel mineral production in the United States was $39.4 billion, with industrial minerals amounting to $29.2 billion, and metals about $10.2 billion, $6 billion of which was derived from copper and gold mining. Nonmetals, coal, and metals accounted for 41 percent of the mineral wealth extracted during the year, with the remaining 59 percent being contributed by higher-priced petroleum, natural gas, and other liquid fuels.

VII

Mine Safety

Mining is a hazardous occupation, and the safety of mine workers is an important aspect of the industry. Statistics indicate that surface mining is less hazardous than underground mining and that metal mining is less hazardous than coal mining. A study of the frequency and severity of accidents shows that the hazards stem from the nature of the operation. In all underground mines, rock and roof falls, flooding, and inadequate ventilation are the greatest hazards. Large explosions are characteristic in coal mines, but more miners suffer accidents from the use of explosives in metal mines. Accidents related to the haulage system constitute the second greatest hazard common to all types of mines.

A number of debilitating hazards exist that affect miners with the passage of time and that are related to the quality and nature of the environment in the mines. Dust produced during mining operations is generally injurious to health and causes the lung disease known as black lung, or pneumoconiosis (see Occupational and Environmental Diseases). Some fumes generated by incomplete dynamite explosions are extremely poisonous. Methane gas, emanating from coal strata, is always hazardous although not poisonous in the concentrations usually encountered in mine air, and radiation may be a hazard in uranium mines (see Radiation Effects, Biological). A tight and active safety program is usually in operation in every mine; where special care is taken to educate the miners in safety precautions and practices, accident rates are lower.

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Federal and state legislation has set numerous operating standards regarding dust and gas concentrations in the mines, as well as general rules regarding roof support. Despite this, local conditions can suddenly change the atmosphere in the mines and render it hazardous. The Federal Coal Mine Health and Safety Act, passed in December 1969 and expanded in 1977, provided health compensation to miners and set strict controls regarding coal dust, methane gas, escapeways, roofing, wiring, and other mining hazards.

Some hazards are related to the local geology and the state of stress in the rocks in the mine. The mining operation results in the shifting of loads on the strata, and in extreme cases such shifts may apply pressures on a critical section of rock that exceed the strength of the rock and result in its sudden collapse. This phenomenon, which is known as a rockburst, occurs particularly in deep mines, and research is under way to eliminate the danger.

Education, experience, research, social consciousness, and government regulation have contributed to lowering the accident rates in the mining industry. In coal mining in the U.S., for example, 346 miners lost their lives in 1930 for every 100 million tons of bituminous coal produced, but in 1990, the number of fatalities was less than one for the same amount of coal. The estimate has been made that 60 to 75 percent of all mining accidents are avoidable and are the result of human error.

Mining operations are considered one of the main sources of environmental degradation. Social awareness of this problem is of a global nature and government actions to stem the damage to the natural environment have led to numerous international agreements and laws directed toward the prevention of activities and events that may adversely affect the environment.

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