Open cast mines

The lignite deposits of North Dakota and Montana extend into Canada as far as Saskatchewan. Canadian deposits are also located in Alberta, Yukon, the Northwest Territories, Ontario, and Manitoba. Production by open-cast mining, ca3.5 x 10 t in 1975, was 10.8 x 10 t in 1989. 

FIGURE 15.7 Secondary changes in the total group composition of soluble organic matter as a result of simulated water washing extracts of the Miocene lignite and shale (both of the Bechatow open cast mine, Poland), the Upper Devonian shale (the Holy Cross Mountains, Poland), and the Upper Carboniferous bituminous coal (the Upper Silesia Coal Basin, Poland). 

Temple, J. M. F. Sykes, A. M. 1992. Asthma and open cast mining. British Medical Journal, 305, 396-397. 

The magmatic deposits (Kola Russia, Phalaborwa South Africa) are extracted in open cast mines or underground mines. They have a high phosphate content and are free of organic impurities. The phosphate ore is extracted together with gangue, which is separated by flotation. 

Raw kaolin is mainly extracted by open cast mining. Secondary deposits can be exploited using excavators, whereas primary deposits of kaolin are often washed out of the rock with a high pressure water jet. 

Standard underground and open cast mining techniques are used for extraction on land. Underwater mining is practised off the coast of Namibia. There diamond-containing clays are sucked up from the seabed and immediately concentrated on site. 

Graphite ore is extracted by underground and open cast mining. Beneficiation takes place by sorting according to carbon content, crushing and enrichment. 

The cassiterite ore is obtained by dredging, open-cast mining, or gravel-washing, in which the ore is washed out of the deposit with high-pressure jets of water. The cassiterite has a density 2.5 times that of sand, and the ore is concentrated by gravity. It is roasted to remove arsenic and sulfur, and to convert metal sulfides into oxides, then it is reduced by smelting with coal or fuel oil in a reverberatory, rotary, or electric furnace (Equation 1.1.1). 

From the ugliness of an open cast mine, to the health problems of mine workers, to the bitter civil wars fought over mineral resources in Africa, the impact of mining... 

A rather special problem can sometimes arise when analyzing certain t)rpes of copper sulfide ore from an open cast mine. In this case it can happen that, close to the surface, where air has been in contact with the sulfide ore, the ore can be oxidized. Thus a particle of chalkopyrite CuFeSa may be converted to CuFeOa. Where the oxidation is limited to the outside of the particle the effect is called rimming the outside of the particle is copper iron oxide, but the inside of the particle is copper iron sulfide. ITie thickness of the oxide layer may be dependent on the depth of the mine from which the ore is being taken. As has been previously stated, while fusion of the sample with a borate flux would probably solve the problem, special circumstances may prevent use of this additional sample preparation step. The problem for the analyst is to judge when special precautions have to be taken. 

Workable apatite deposits occur mostly near the earth s surface in sfiata varying from a few inches to over 30 ft. About 80% of the world s phosphorite is obtained by open-cast mining methods. 

Open-cast mines They are surface mines in which the stripped overburden is not removed from the mine to be dumped in a separate disposal area, but is cast (i.e. hauled and dumped) inside the mine from where the desired material is already worked. 

The areas of open-cast mines were reclaimed after closure of the mining activities, and by 1992 up to 382 km were recovered in the Lusatian district. Of... 

The open-cast mining lakes in the area of the former G.D.R. show the full scale from neutral to very acidic lake waters. Especially in the Lusatian lignite district some, large lakes exist for about four decades, remaining very acidic without... 

M. Schultze and W. Geller Table 8.4. List of 21 open-cast mining lakes in the former G.D.R. depicting pH-values and concentrations of iron and aluminium as investigated in July 1993 (and in September 1992) ... 

The only major bulk chemical not so far considered is phosphoric acid, which can be manufactured pure from phosphorus and in an impure form from phosphate rock. The latter process is the dominant one, the impure product being used mainly in the preparation of fertilizers. Phosphate rock is also the most common source of elemental phosphorus. It is extracted by open-cast mining. The thermal process for producing phosphoric acid from the element produces an acid which is about three times more expensive than that produced direct from phosphate rock using the so-called wet process. 

FIGURE 36.1 Open cast mining in the Magok region of Myanmar (Burma). 

The application of seismic networks for monitoring slope conditions at open-cast mines has generated abundant data in the event of slope failure. An enormous 65 x 10 m landslide occurred at the Bingham Canyon copper mine in the USA in 2013 (Pankow et al. 2014). In this case, seismometers that detected the event were located between 6 and 400 km. The landslide, classified as a rock avalanche, was actually two closely spaced events. The seismicity was dominated by long-period events with differences between the two episodes only the first one produced a high-amplitude peak near the end of the coda and there was a large difference when the maximum amplitude occurred. 

The lecoveiy of natural resources from the Earth s crust is an important activity, in which sintered hard metals play a cracial role. It relates to both underground and open cast mining techniques for the recoveiy of minerals - metallic and non-metallic - like carbon (coal), potash, natron, gypsum and of course petroleum drilhng (petroleum, natural gas). The methods of evacuation and the types of tools used depend on the type of stratification encountered. We can classify drilhng into three types ... 

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