process control diagram of open cast gold mining

reading: open-pit mining | geology

This form of mining differs from extractive methods that require tunneling into the earth, such as long wall mining. Open-pit mines are used when deposits of commercially useful minerals or rocks are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling (as would be the case for sand, cinder, and gravel). For minerals that occur deep below the surfacewhere the overburden is thick or the mineral occurs as veins in hard rockunderground mining methods extract the valued material.

Open-pit mines are typically enlarged until either the mineral resource is exhausted, or an increasing ratio of overburden to ore makes further mining uneconomic. When this occurs, the exhausted mines are sometimes converted to landfills for disposal of solid wastes. However, some form of water control is usually required to keep the mine pit from becoming a lake, if the mine is situated in a climate of considerableprecipitation or if any layers of the pit forming the mine border productive aquifers.

Open-cast mines are dug on benches, which describe vertical levels of the hole. These benches are usually on four to sixty meter intervals, depending on the size of the machinery that is being used. Many quarries do not use benches, as they are usually shallow.

Most walls of the pit are generally dug on an angle less than vertical, to prevent and minimize damage and danger from rock falls. This depends on how weathered the rocks are, and the type of rock, and also how many structural weaknesses occur within the rocks, such as a faults, shears, joints orfoliations.

The walls are stepped. The inclined section of the wall is known as the batter, and the flat part of the step is known as the bench or berm. The steps in the walls help prevent rock falls continuing down the entire face of the wall. In some instances additional ground support is required and rock bolts, cable bolts and shotcrete are used. De-watering bores may be used to relieve water pressure by drilling horizontally into the wall, which is often enough to cause failures in the wall by itself.

Ore which has been processed is known as tailings, and is generally a slurry. This is pumped to a tailings dam or settling pond, where the water evaporates. Tailings dams can often be toxic due to the presence of unextracted sulfide minerals, some forms of toxic minerals in the gangue, and oftencyanide which is used to treat gold ore via the cyanide leach process. This toxicity can harm the surrounding environment.

After mining finishes, the mine area must undergo rehabilitation. Waste dumps are contoured to flatten them out, to further stabilise them. If the ore contains sulfides it is usually covered with a layer of clay to prevent access of rain and oxygen from the air, which can oxidise the sulfides to producesulfuric acid, a phenomenon known as acid mine drainage. This is then generally covered with soil, and vegetation is planted to help consolidate the material. Eventually this layer will erode, but it is generally hoped that the rate of leaching or acid will be slowed by the cover such that the environment can handle the load of acid and associated heavy metals. There are no long term studies on the success of these covers due to the relatively short time in which large scale open pit mining has existed. It may take hundreds to thousands of years for some waste dumps to become acid neutral and stop leaching to the environment. The dumps are usually fenced off to prevent livestock denuding them of vegetation. The open pit is then surrounded with afence, to prevent access, and it generally eventually fills up with ground water. In arid areas it may not fill due to deep groundwater levels.

Gold is generally extracted in open-pit mines at 1 to 2ppm (parts per million) but in certain cases, 0.75ppm gold is economical. This was achieved by bulk heap leaching at the Peak Hill mine in western New South Wales, near Dubbo, Australia.

Nickel, generally as laterite, is extracted via open-pit down to 0.2%. Copper is extracted at grades as low as 0.15% to 0.2%, generally in massive open-pit mines in Chile, where the size of the resources and favorable metallurgy allows economies of scale.

open pit mining techniques|surface mines|rock or mineral extraction

Open-pit Mining Open-pit mining, also known as opencast mining, open-cut mining, and strip mining, means a process of digging out rock or minerals from the earth by their elimination from an open pit or borrow. The word is used to distinguish this type of mining from extractive methods that need tunneling into the earth. Open-pit mines are used when deposits of commercially helpful minerals or rock are found close to the surface; that is, where the overburden (layer material covering the valuable deposit) is comparatively thin or the material of interest is structurally inappropriate for tunneling. For minerals that happen deep underneath the surface-where the overstrain is solid or the mineral happens as veins in hard rock- underground mining methods take out the precious material.

Open-pit mines that manufacture building materials and dimension stone are usually referred to as quarries. People in few of the English-speaking countries are not likely to make a difference among an open-pit mine and other kinds of open-cast mines, like quarries, borrows, placers, and strip mines. Open-pit mines are characteristically engorged until either the mineral resource is exhausted, or a mounting ratio of overburden to ore makes more mining uneconomic. When this occurs, the exhausted mines are at times converted to landfills for disposal of solid wastes. Nevertheless, some form of water control is normally required to keep the mine pit from becoming a lake. Open Cut mines are dug on benches, which portray vertical levels of the hole. These benches are normally on four meter to sixty meter intervals, relying on the size of the machinery that is being utilized. A lot of quarries do not use benches, as they are normally shallow. Most walls of the pit are normally dug on an angle less than vertical, to avert and lessen damage and hazard from rock falls. This relies on how weathered the rocks are, and the kind of rock, and also how a lot of structural weaknesses happen within the rocks, like a fault, shears, joints or foliations.

The walls are stepped. The inclined part of the wall is called the batter, and the flat part of the step is called as the bench or perm. The steps in the walls help avert rock falls continuing down the entire face of the wall. In some instances additional ground support is needed and rock bolts, cable bolts and shotcrete are utilized. De-watering bores might be used to ease water pressure by drilling horizontally into the wall, which is frequently sufficient to cause failures in the wall by itself. A haul road is located at the side of the pit, forming a ramp up which trucks may drive, taking ore and waste rock. Waste rock is piled up at the surface, near the edge of the open cut. This is known as the waste dump. The waste dump is also tiered and stepped, to lessen degradation. Ore which has been processed is called as tailings, and is normally slurry. This is pumped to a tailings dam or settling pond, where the water fades away. Tailings dams may frequently be toxic due to the presence of unextracted sulfide minerals, few types of toxic minerals in the gangue, and frequently cyanide which is utilized to treat gold ore via the cyanide leach method.

Looking at what the nature has to offer, it conveys a lot of information when it comes to things that it holds in it, within it and on it. With need for minerals and its wide spread application getting widened each day, the stint of its very existence is getting blink and its depreciation in its source which is its over usage is on the high.

literally means extraction .Our Mother Earth has lots of resources deep within her and mining is the method of extracting all these valuable resources from the earth through different means.There are different methods to extract these resources which are found in different forms beneath the earth's surface.

The metal mining was one of the traditions that have been passed on meritoriously over the past years so that we meet our day-to-day needs of the desired material usage starting from the equipments that are ornamental as well as purposeful coordination of information's.

Jadeite is a pyroxene mineral and is one of the two types of pure jade. The other is known as nephrite jade. Jadeite is the rarer of the two jades, and as a result, it is considered to be more precious and valuable. Due to its striking and emerald green color it is also known as "imperial jadeite".

Surface mining is basically employed when deposits of commercially viable minerals or rock are found closer to the surface; that is, where overstrain (surface material covering the valuable deposit) is relatively very less or the material of interest is structurally unsuitable for heavy handling or tunneling.

Underground mining is carried out when the rocks, minerals, or precious stones are located at a distance far beneath the ground to be extracted with surface mining. To facilitate the minerals to be taken out of the mine, the miners construct underground rooms to work in.

Gold is a chemical component with the symbol Au that springs up from the Latin derivative aurum that means shining dawn and with the atomic number 79. It is a very sought-after valuable metal which, for many centuries, has been utilized as wealth. The metal resembles as nuggets or grain like structures in rocks, subversive "veins" and in alluvial deposits. It is one of the currency metals.

Platinum, is a heavy, malleable,ductile, highly inactive, silverish-white transition metal. Platinum is a member of group 10 elements of the periodic table.It is one among the scarce elements found in Earth's crust and has six naturally occurring isotopes. It is also achemical element.

Diamonds and supplementary valuable and semi-precious gemstones are excavated from the earth level via 4 main types on mining. These diamond withdrawal methods vary depending on how the minerals are situated within the earth, the steadiness of the material neighboring the preferred mineral, and the nonessential damage done to the surrounding environment.

an overview of the open pit mining process

There are two types of mining methods commonly used in large scale mineral mining; open pit mining and tunneling. Open pit mining is used when the minerals to be mined are located just close to the surface. This is especially when the soil or material covering the minerals are relatively thin and can easily be moved for the mining to take place.

Open-pit mines are usually operated until either the mineral asset in them is depleted or expanding the mines becomes uneconomical to sustain. At such a point when this happens, the depleted mines are in some cases changed over to landfills for disposal of wastes.

Some type of water control is generally required to keep the pits for the open pit mine from turning into a lake; this is especially important if the mine is located in a climate with considerable precipitation or if the geological makeup of the mine allows for underground water movement.

Open-cast mines are burrowed on benches, which depict vertical levels of the pit. These benches are usually excavated at between four and sixty-meter intervals. The size of the benches depends on the size of bulldozers used to make them.

Most of the open pits mines used to produce building materials (quarries) are usually shallow and thus dont have benches. The walls of the pits are excavated at an angle to minimize the dangers associated with having vertical walls such as falling rocks. This is determined the nature of the rocks especially their weathering and structural weaknesses such as foliations, shears, and faults within the area.

The walls to the pits are usually stepped. The flat part of the wall steps is known as the berm or bench while the slanted segment of the walls is known as the batter. The creation of steps in the walls is meant to help prevent rocks falling. Sometimes rock bolts, shotcretes, and cable bolts are used to create additional support for the walls. De-watering drills might be used to help mitigate water weight by boring on a level plane into the walls, which might affect the strength of the walls.

Other than strong walls, open pit mines are made with a strong haul road which is generally built along the edge of the pit, in the form of a gradual slope up from the bottom of the pit on which trucks can drive up carrying both minerals and waste rocks. The waste rocks are heaped up on the surface, close to the edge of the open pit in what is commonly referred to as the waste dump. The waste dump is likewise layered and stepped, to slow down degradation.

Tailings dams can be poisonous because of the presence of toxic materials such as unextracted sulfide minerals, several types of harmful minerals in the gangue, and most often cyanide which is utilized to treat gold ore using the heap leaching process. This poisonous materials can be harmful to the encompassing environment if not managed properly.

When the mineral in the open pit is depleted, the mine need to undergo rehabilitation. Some of the time, abandoned open pits are used as dumping for solid waste. In the event that the mined ore contained sulfides it is secured with a layer of mud to be used avert access of rainwater and oxygen from the air, which can oxidize the sulfides to produce sulfuric acid. The mine is then covered with soils and vegetables planted over it to recover the natural look of the area.

Mine rehabilitation is an important step in the process of developing a mine, and most countries require a plan in place to to rehabilitate the land following a mining operation, although not all countries have the same requirements. 3rd world countries are generally much more relaxed about regulations than some of the major gold mining countries such as Canada, Australia, or the United States.