The reason why it is necessary to smelt metals is that they react with other materials like oxygen, sulfur etc to form compounds. Only a small number of unreactive metals, like gold for instance, occur native (naturally as the metal itself). As the best grade ores are extracted and smelted, that leaves us with only the lower grade ores to satisfy demand and so the price of metals has risen. Also, some ore will have been thrown out with the mining and processing waste, so this waste is effectively a low grade ore too. As they have become more expensive, methods of obtaining metals from these... Show more

The reason why it is necessary to smelt metals is that they react with other materials like oxygen, sulfur etc to form compounds. Only a small number of unreactive metals, like gold for instance, occur native (naturally as the metal itself).

As the best grade ores are extracted and smelted, that leaves us with only the lower grade ores to satisfy demand and so the price of metals has risen. Also, some ore will have been thrown out with the mining and processing waste, so this waste is effectively a low grade ore too. As they have become more expensive, methods of obtaining metals from these lower grade ores have been developed. These new mining methods can recover metals from low grade ores and waste, for example by phytomining using plants and bioleaching using microorganisms. The big disadvantage of these methods is the speed at which they work - much more slowly than conventional 'dig the ore out of the ground' methods. This makes them relatively expensive but, as long as the price of a metal is also expensive, it makes using them worthwhile to the mining companies.

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