In these mines, the gold is extracted from the rock where it was originally deposited. Some hardrock mines are underground mines.
A tunnel is drilled or blasted to the source of the ore, which is transported out for processing often by truck or rail. A variety of specific techniques can be used for mining the ore, depending on the geology of the area - such as block caving , which allows massive strip-mine scale underground excavation, or the more steretypical cut-and-fill and drift-and-fill techniques, where miners dig our out in long horizontal tunnels.
Other hardrock mines are large strip mines that remove the surface dirt and rock and then extract the ore from the resulting open pit. Removal of ore is often accomplished explosives, enormous power shovels , and massive trucks, some capable of carrying tons of rock in one load. In both kinds of hardrock mining, the ore is then processed in some manner to remove the gold.
Usually this entails crushing the rock into powder and using some combination of gravity, centrifugation, and "froth flotation" to perform an initial separation of gold from rock. In many cases this is followed by some form of cyanide treatment to precipitate out the remaining gold. The remaining ore mud waste is known as "tailings" , the disposal of which is one of the largest challenges facing a hardrock mine.
Gold is both highly valuable, and relatively useless. The vast majority of gold mined throughout history is now jewelry, or stored in vaults as an investment This means that governments are in effect lowering the cost of environmentally destructive mining, contributing to demand by hoarding large reserves, and then directly paying for the costs of mine cleanup.
Copper ore with a content of 0. This is because extraction costs are lower in an open pit at the surface than in an underground mine. In an open pit, more low-grade ore can be extracted with a lower content, while underground mines mean more expensive operation. If deposits with a higher concentration are found at great depth however, underground mines can be profitable.
In Sweden there are mines reaching depths of more than 1, m. The location of the deposit decides which type of mine can be set up. For example, an open pit mine cannot be started if the deposit is at a depth of 1, m. The quantity of ore extracted every year, the rate of extraction, differs between different types of mine. An open pit means that more ore can be extracted at a lower extraction cost.
The offer also means that lower ore content can be extracted, which means that more ore must be extracted every year to achieve profitability in the mine. This is the case for example with the open pit called Aitik, where large quantities of low-grade ore are extracted. In the small underground Lovisa mine a small quantity is extracted each year, but comprises more high-grade ore. The size of the mine depends on several factors, among other things how large the deposits are, how large the investment is, the mining method and so on.
In general, ore can be divided into three types: sulphide ore, iron ore and gold ore. The types of ore differ among other things in how they are processed, their composition and their general environmental impact. Sulphide ore consists of sulphur compounds. Sulphide mineral is mineral comprising sulphur compounds. Such compounds that are of economic interest include zinc blende, lead glance and chalcopyrite.
Several base metals, such as zinc, lead, copper and nickel, are extracted from sulphide ores. Even gold and silver can be extracted from them, often as by-products. Since sulphide ore contains large quantities of sulphide minerals, they are often associated with greater environmental risks than many other ores. This is because all sulphide minerals weather or decompose quickly in contact with oxygen.
Read more about sulphide mineral in the fact box on the next page. It is often only iron that is extracted from iron ore, but there can be other metals and substances in the ore. There are several types of iron ore minerals, magnetite and haematite ore being the most important. In Sweden, most of the iron ore is extracted from so-called apatite iron ore. It takes its name from the high content of apatite mineral, which contains phosphorus.
The apatite iron ores in the active mines contain about 70 per cent iron. They always have a very low content of sulphide mineral and are therefore generally less hazardous to the environment. In Sweden there are also skarn iron ores, which unlike apatite iron ores can contain large quantities of sulphide mineral. Gold often occurs together with other metals such as silver and platinum metals, but can also occur in among other things sulphide minerals. Several of the most important gold ores are formed in gold seams in quartz or other valuable types of rock.
Gold is also extracted largely from older sedimentary placer strata and sulphide ores. The content of sulphide mineral in gold ore varies. Gold ores can however also produce hazardous waste. The proportion of tailings occurring is related to the content in the ore. Iron ores, which have a high content often over 30 per cent generate less tailings than sulphide ores which are often of a lower grade from 0.
Early exploration in Finland, investigating soil samples. The geologist dug the samples and carried the till samples and Reino the dog carried geochemical samples and drinking water. Click here to cancel reply. Name required. Email will not be published required. When it comes to buying the right equipment for your mining operation, there are a number of factors to consider.
Every day, 6, people die as a result of occupational accidents or work-related diseases. World Safety Day helps raise awareness of occupational safety and health.
Through worldwide events and activities on World […]. Thousands of key players in the mining and metallurgy market gathered to exchange ideas and discover new technologies to improve their extraction processes. There are several techniques and processes by which gold may be extracted from the earth. Placer mining Placer mining is the technique by which gold that has accumulated in a placer deposit is extracted.
Placer deposits are composed of relatively loose material that makes tunneling difficult, and so most means of extracting it involve the use of water or dredging.
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