According to archaeologists, man has been doing basic mining as early as 3000 B.C. The first two metals ever discovered are copper and gold with the former dating back to 8,700 B.C. The four most widely consumed metals are iron, aluminum, copper, and zinc.
An American uses an average of 40,000 pounds of new minerals each year and the U.S. state that produces the most coal is Wyoming.
Types of Mining
Block caving is a general term and usually has to do with a mass-mining system that relies on gravity to extract the ore deposits. A thin horizontal layer at the mining level of the ore column is removed, then due to gravity, the ore caves. One broken ore is removed from the ore column’s mining level, while the ore above it continues to break and cave by gravity. The term “block caving” likely started in mines with porphyry copper in them, where it was mined by being divided into rectangular blocks which were then mined in a checkerboard pattern. All of the ore in a block was removed before any adjacent blocks were mined. Although mining is now done using a panel system, whereby the panels are mined either sequentially or by other methods, the term is still used for any type of mining that uses gravity. There are also three major types of block caving, including:
- The grizzly or gravity system. In this method, the ore from the draw-points flows to the transfer raises after sizing at the grizzly. It is then gravity-loaded into ore cars.
- The slusher system. This method uses slusher scrapers for the main production unit.
- The rubber-tire system. In this method, load-haul-dump (LHD) units are used for the main production unit.
Of all the mine exploitation systems, block caving has the lowest cost, except for maybe open-pit mining or in-situ recovery.
A method of short-hole mining, cut-and-fill mining is used in irregular or steeply dipping ore zones, especially where the hanging wall limits the use of long-held methods. The ore is mined either in slightly inclined or horizontal slices then it is filled with sand, waste rock, or tailings. This method is used in the construction of canals, roads, and even railways, and the amount of material from cuts matches the amount of fill required to make nearby embankments. This minimizes the amount of construction labor. Cut slopes are usually more than a slope of two-to-one in horizontal-to-vertical dimensions. With cut sections of rails or roadways, the roadway is lower in elevation than the terrain that surrounds it.
Operationally, unique environmental effects associated with cut sections of the roadway are sometimes significant. An example of this occurs when, due to the cut section, air pollutants might concentrate in the valleys created by those sections. On the opposite end, noise pollution can actually be mitigated by cut sections, mainly because the depressed roadway design creates an effective blockage of any line-of-sight sound propagation.
Cut-and-fill mining is a favorite among mining groups that want the capability to adapt to variations within the rock mass, as well as for those that experience sometimes irregular and steeply dipping ore bodies. Generally known as a small-scale mining method, this mining takes place in horizontal slices found along the ore body, and the bottom slice is the first to be mined. The excavated area is backfilled next, and then production continues upwards. With each production level, constant drifting occurs until the entire slice is mined, after which the slice is backfilled, and the fill becomes the platform that begins the next mined level.
Dredging involves the removal of material from one part of the water environment and the relocation of it to another. In most situations, the excavation is handled by specialist floating plants, called dredgers. Many different locations and many different purposes are associated with dredging, but the main purpose is normally the recovery of material that has some type of use or value or to create a bigger depth of water. The different types of dredging machines include:
- Suction dredgers: this includes trailing-section, cutter-suction, auger-suction, jet-lift, and air-lift dredgers.
- Mechanical dredgers: these include grab, bucket, bed-leveler, backhoe/dipper, krabbelaar, pneumatic, snag-boat, water-injection, amphibious, submersible, and fishing dredgers.
In highwall mining, which originated from the auger type of mining, continuous miners, instead of augers, are used to bore an adjacent entry to the coal seam of a high wall that was left behind after an excavation has been completed in an open pit mine. Screw conveyors, which are located behind the continuous miner, haul the already cut coal from deep within the seam to a stockpiling area located outside, then it is transported to another area. Highwall mining differs from continuous mining in that it is carried out by remote control at the surface. Here, an operator, usually located in a cabin, uses a television monitor to control the progress of the continuous miner machine.
Highwall mining is often used when excavating an open-pit mine becomes too expensive. There are many advantages over underground mining, including the fact that it is both more cost-effective and involves less lead time. Highwall mining is also safer than other types of mining, and when, it occurs at the surface, it often produces the same amount of output as mining underground does. Smaller blocks of coal can be accessed with highwall mining, and operations can take place around structures or geological impediments that may otherwise impinge upon the production of coal.
In Situ Mining
Also called in-situ leaching, or ISL, as well as in-situ recovery (ISR) and solution mining, this process is usually used to recover minerals such as uranium and copper. This is done through boreholes which are drilled into a deposit, in situ. The steps involve artificially dissolving the minerals that occur naturally in a solid state. Initially, the holes are drilled into the ore deposit. Pathways are then created through hydraulic or explosive fracturing in order for the solution to penetrate. Next, the leaching solution is pumped into the deposit, and it makes contact with the ore. The dissolved ore content that contains the solution is then pumped to the surface, where it is then processed. This is a process that allows for salts and metals to be extracted from an ore body without using the conventional mining processes that usually involve open-cut, drill-and-blast, or underground mining.
Minerals that are mined through in-situ mining include:
- Soluble salts and potash
Longwall mining involves underground coal mining, whereby a long wall of coal is mined via a single slice, and the slice is usually from two feet to a little over three feet thick. The block of coal being mined, which is called the longwall panel, is normally approximately 270 to 430 yards in width and two to three miles in length. Before longwall mining begins, gate roads are driven to the back of each panel, called the main gate or headgate, and the tailgate. If the coal’s thickness allows it, the gate roads are developed by continuous miner units beforehand. There are two types of longwall layouts: the retreat type and the advancing type.
The advancing type of longwall has gate roads that are formed as the coal face advances. In the retreat type, the panel connects the two of them and is a face. Only the main gate is formed before the face is. The tailgate road forms behind the coal face when the stone above the coal height is removed in order to form a roadway that is high enough for the miners to travel in. The “face” is the end of the block, including the longwall equipment. The other end of the block usually includes one of the mine’s main travel roads, and there is a cavity behind the longwall called the gob, although there are other names for it.
Mountaintop Removal Mining
Mountaintop removal mining refers to any method of surface coal mining whereby a mountaintop or ridgeline is destroyed, regardless of whether the mined area is going to be returned to what is known as its “approximate original contour.” There are different methods of mountaintop removal coal mining, including the box-cut method, steep-slope method, cross-ridge method, and a few others. Mountaintop removal involves several steps, as described below.
- The vegetation and topsoil of the mountaintop are removed first. The trees are then destroyed, usually by burning or some other method.
- In this step, blasting is used to blow up the top of the mountain, and it can remove up to 600 feet or more of elevation.
- Digging is the next step, and earth-moving machines are used to remove all of the coal and debris. In this step, the machines can be expensive, but they save money because they replace hundreds of miners.
- The waste is then dumped into “valley fills.”
- The coal is processed before it is shipped to power plants, and this usually involves being treated with chemicals ahead of time.
Mountaintop mining occurs in eastern Kentucky, southwestern Virginia, eastern Tennessee, and southern West Virginia. Much like other mining methods, it is a bit controversial, but it isn’t likely to end anytime soon.
Known as opencast mining in areas outside of the United States, the process involves digging out minerals or rocks by eliminating them from a borrow or open pit. It is called open pit to distinguish it from mining methods that use extractions that include tunneling into the earth. When minerals or rocks that are good for commercial purposes are found close to the surface, open-pit mines are used. This method can also be used if it is structurally impossible to choose the tunneling method or when the layer of material that covers the valuable deposit is very thin. If minerals are found deep underneath the surface, underground mining methods remove the precious material.
If open-pit mines make dimension stone and building materials, they are often called quarries. They can also be called borrows, strip mines, or even placers. In many cases, open-pit mines are engorged until the mineral resources are removed or if it becomes economically difficult to mine there. Sometimes, the exhausted mines are converted to landfills, but, in most cases, a form of water control is necessary so that the mine pit doesn’t become a lake.
Open-pit mines are dug on benches, displaying vertical levels of the hole. The benches are usually spaced at 13- to nearly 200-feet intervals apart, and they rely on the size of the machinery used in the process. However, some shallow quarries do not use the benches.
Most pit walls are dug on angles that are less than vertical in order to lessen and avert the hazard from falling rocks. This depends on how weathered the rocks are and their type. The walls are stepped, and the steps help avert falling rock from continuing down the face of the wall. In certain situations, more ground support is needed, in which case cable bolts, rock bolts, or even shotcrete are used. Dewatering bores can be used to ease water pressure, which is done by drilling horizontally into the wall. This prevents failures of the wall on its own.
Haul roads are usually found on the side of the pit, which forms a ramp that trucks can drive up, where they can remove waste rock and ore. A process known as waste dump can also be utilized, and this involves waste rock being piled up at the surface, near the open cut’s edge. The waste dump is both stepped and tiered in order to ease degradation.
Tailings, which is processed ore, is pumped to a settling pond or a tailings dam, allowing the water to fade away. Tailings dams are often toxic thanks to the unextracted sulfide minerals present. They can also be toxic due to the cyanide which is sometimes used to treat gold ore or the toxic minerals in the gangue.
Room-and-Pillar Underground Mining
This form of mining involves mining the coal seam in a checkerboard style, which leaves pillars of coal that support the roof. This, in turn, makes it faster to get to the coal access with low invest, when compared to longwall mining. In room-and-pillar mining, however, only 50% to 75% of the coal reserves are utilized. Room-and-pillar mining is used to develop roadways so that the miners can prepare the coal face for longwall operation. In this type of mining, continuity is imperative if you want to make a profit. The coal is usually cut via a continuous miner that delivers the product to hollers. The product is brought to feed a breaker unit and to prepare and deliver it onto the belt system. Feeder breakers are moved only once in a while; however, the other equipment is in constant motion in order for the maneuverability cable to be operational and the maximum load capacities to be vital.
There are two basic types of mining: mining underground and mining at the earth’s surface. Nearly two-thirds of the world’s solid minerals are mined through surface mining. It is especially predominant in obtaining items such as coal, copper, sand, gravel, crushed stone, iron, aluminum, and phosphates. There are five basic types of surface mining, including open-pit mining, strip mining, dredging, mountaintop removal, and highwall mining. All of these methods remove the waste material or the overburden, that is above the desired resource.
Often, surface mining is preferred over underground mining, or subsurface mining, for numerous reasons. This type of mining produces fewer complications regarding water and electricity, it is much less expensive, and it is safer than these other types of mining.
The Advantages of Coal and Mineral Mining
It Creates Employment for a Lot of People
Mining always creates both primary and secondary employment opportunities for people. The primary opportunities include numerous onsite jobs that are performed by local citizens. The secondary opportunities include specialized posts that require top-notch experts from other countries. In fact, the mining business has allowed some countries to get rid of their unemployment altogether.
It is an Economy Booster
Both the local economy, in other words, the area where the mining is actually taking place, and the country’s economy are boosted when mining facilities are developed and utilized. These boosts include employee salaries, money from taxes and fees, royalties, and the economic activity due to the purchase of goods and services. This enhanced economy also means better amenities because the government ends up having more money to spend. In other words, people and entities are making money, which is always good for the economy, both local and national.
It Increases Investments Coming in From Other Areas
Mining can actually encourage countries to take part in another country’s development. This is accomplished mostly through the building of factories by foreign investors, as well as through the enhancement of mineral exports. Increased foreign investment always results in a better tolerance among neighboring nations, and, of course, the economic impact for all countries involved cannot be understated.
It Earns Foreign Exchange
Some minerals, including diamonds and gold, are sometimes used as a type of currency. Gold-mining, in fact, benefits a nation’s economy because it is possible for it to quickly take over conventional exports. In addition, the home country can earn foreign currencies whenever other countries purchase your minerals, which it can use on things such as new machines and foodstuffs.
It Supplies Many Important Raw Materials
Mining provides raw materials such as coal and various metals, among others, that are necessary to build and maintain modern-day economies and industries. In fact, mining is essential to the society everyone enjoys today. The items produced by mining efforts are used in thousands of products that are used every day, including computers and other technology products. Even the electricity in your home may come from either the oil, gas, or coal that has been brought from under the ground.
Other Benefits of Mining
Mining enables the miners to possibly find something new and very valuable because they never know what might turn up while they’re digging. It also allows people to obtain useful elements that come with a significant profit, which cannot be overlooked. In addition, because coal is so readily available in the United States and many other parts of the world, especially when compared to other petrochemicals, it is easy to find and easy to utilize.
Since most of the coal and metals found through mining are solids, they transport very easily and rarely cause any spills or other types of harm to the environment. These products also store very easily, and you can store them safely and in very large quantities. This means it is also easy to transport the products over long distances, and many different cities and municipalities can enjoy its benefits.
Last, you cannot overestimate the cost of mining, which is relatively inexpensive in most cases. Especially with coal, most mining processes are very inexpensive to utilize, and, since some mining methods are cheaper than others, it is possible for a region or city to choose the type of mining that is most likely to be cost-effective and produce the greatest results.
Glossary of Mining Terms
Aquifer: A water-bearing bed made up of sandstone or some other type of porous rock.
Auger: A rotary drill with a screw device that is used to break, penetrate, and transport drilled material, which is usually coal.
Cage: A device found in a mine shaft that looks like an elevator car and is used for hoisting materials and personnel.
Kerf: A coal face’s undercut.
Nip: A device found at the end of a mining machine’s trailing cable that is used to connect the trailing cable to the ground and trolley wire.
Outcrop: Coal that is found either near or at the surface.
Roof Sag: This is when a roof sinks, curves, or bends from pressure or weight, particularly if it does so in the middle section.
Seam: A bed or stratum of coal.
Sounding: The process of knocking on a roof in order to determine whether it is safe and sound to work under.