EXPLOITING MINERAL RESOURCES

EXPLOITING MINERAL RESOURCES

The minerals have to be exploited profitably, if their economic worth is to be realised. The profitability of mining operations depends on the value of the mineral and mining the costs. The mining costs would depend on the size of the deposit; grade of the ore; method of mining; transport and labour cost; and availability. Minerals occUr in varied formations, so different methods are needed to extract them from the surrounding rocks.

Open-cast mining is the easiest and the cheapest way of mining minerals occurring near the surface. The over­burden (the earth or other rock bands lying above the mineral-bearing strata) is removed and the ore is extracted layer by layer till the mineral content becomes too small or the pit becomes too deep for economic mining. Quarrying rock sucn as limestone, gravels, igneous rocks, and clay for bricks, involves open-cast methods.

When the ores lie deep below the surface, under­ground mining methods have to be used. Simple adits or inclined tunnels may be sufficient; however, often enough, vertical shafts have to be sunk to reach mineral seams. In case of minerals such as salt, potash, or sulphur, pipes are to be drilled down to the deposits and superheated steam or water injected to dissolve the minerals. The liquid is then pumped to the surface, where the water is evaporated to leave behind the mineral.
Minerals occurring in alluvial deposits are usually recovered by placer mining methods. The alluvium is mixed with plenty of water and then the mixture is rotated till the lighter particles (sand, mud, dust, stones) are washed off. The heavier ores with greater specific gravity are left behind and can be separated. In small deposits or stream beds, the method employed is panning. The disadvantages of panning are: creation of waste material, pollution and silting up of rivers. When alluvial deposits occur on the side of a valley or as a thick terrace deposit, hydraulic mining is employed.

Mining can have harmful effects: it can cause lands to become derelict, leading to wastage of agricultural and industrial land, besides endangering health and physical well-being. Abandoned mines often subside and lead to house collapse. The landscape is left ugly and desolate.