If a vertical shaft or tunnel can be used to reach a mineral deposit, the generally lower cost of driving a tunnel dictates the savings in the cost of pumping water and the ease of lifting the ore through the shaft in favor of the tunnel. Therefore, tunnels as long as one to three kilometers (one or two miles) are often economically feasible. Most tunnels are designed to be slightly inclined upwards from the entrance, allowing water to flow freely from the mine. [5] Mines with tunnels may be drained of water, at least in part, by gravity alone or by force-assisted gravity. The depth at which a mine can be drained by gravity alone is defined by the deepest open tunnel called a drainage tunnel. [6] The term mining dewatering tunnel is also common, at least in the United States. Mining operations above this level (called “above the tunnel”) will remain unchanged until the tunnel is blocked. All pit work under the drainage tunnel (“under the tunnel”) and the groundwater level will be flooded unless mechanical means are used for drainage. Until the invention of the steam engine, this was the main limitation of civil engineering. Tunnels are useful for deeper mines, as water only needs to be lifted at the level of drainage tunnels and not at the surface. The word adit comes from a Latin word meaning approach or entry. Requirements for tunnels vary depending on the construction of the tunnel. Access to a mine through tunnels has many advantages over vertical access shafts used in shaft mining.

Less energy is required to transport miners and heavy equipment inside and outside the mine. It is also much easier to get ore or coal out of the mine. Horizontal travel by narrow gauge railway or cable car is also much safer and can move more people and ore than vertical elevators. In the past, horses and pit ponies were used. A tunnel can also serve as an additional path in the tunnel. This may be necessary in an emergency to recover equipment or to support or rescue tunnel workers. Drainage is another reason to build a horizontal tunnel to an existing tunnel. But the extra passage can also be part of the normal design of the operation.

Drift: A horizontal tunnel that is driven along an ore deposit, either from a tunnel or from a shaft to access the ore. Due to the sharp reduction in operating costs that a drainage tunnel can provide, they have sometimes been driven over long distances for this purpose. One example is the Milwr Tunnel in North Wales, which is about 16 km (ten miles) long. Other examples include the Great County Adit in Cornwall, a 40-mile (65 km) tunnel network that drained the entire Gwennap Mining District, and the 3.9-mile (6.2 km) Sutro Tunnel at Comstock Lode in Virginia City, Nevada. A side effect of driving such extensive tunnels is that previously unknown ore deposits can be discovered, helping to finance the huge costs. [6] In combination with shafts, tunnels form an important element in the ventilation of a mine: in simple terms, fresh air enters through a tunnel, is heated by the higher temperature underground and is naturally drained by vertical shafts, some of which are lowered specifically for this purpose. [4] A tunnel (from the Latin aditus, entrance)[1] is an entrance to a horizontal or almost horizontal underground mine,[2] through which the mine can be entered, drained by water[3] and minerals extracted at the lowest appropriate level. [1] Tunnels are also used to search for mineral veins. [1] The size and cross-section of a stud depends on its use, with the shape of a horseshoe being particularly common. Walls can be made of natural raw rock or lined with concrete, wood or steel. Tunnels can only be dug in a mine if the local topography allows it. For example, there will be no way to dig a tunnel to a mine located on a large flat plain.

Even if the soil is low, the cost of securing a long tunnel can outweigh the potential benefits. Since safety is a top priority in any tunnel construction project, it goes without saying that the free flow of fresh air is crucial when workers are working in a tunnel. Short horizontal tunnels driven into the ground for this purpose are called adits. Tunnels are driven into the side of a hill or mountain and are often used when an ore deposit is inside the mountain but above the bottom of the adjacent valley or coastal plain. In cases where the mineral vein opens on the surface, the tunnel can follow the vein or vein until it is worked, in this case the tunnel is rarely straight. The use of tunnels for ore mining is generally referred to as tunnel mining. Stoll, a horizontal or nearly horizontal passage that is conduit from the earth`s surface into the side of a ridge or mountain to treat, aerate or remove water from a mine. A tunnel is a horizontal or almost horizontal passage to a larger underground excavation for the purpose of aeration, water removal or auxiliary inlet. Short tunnels are used both in mining and tunnel construction to reach the main shaft at strategic points. Crop re-cultivation: The process by which land disturbed by mining activities is reclaimed for beneficial land use. Crop re-cultivation activities include the removal of buildings, equipment, machinery and other physical remains of mining, the closure of tailings piles, leaching platforms and other mining elements, and the contouring, covering and regreening of waste rock piles and other disturbed areas. Gangue: Non-precious materials associated with mineralized minerals.

Semi-autogenous grinding (SAG): the process of grinding fine powdered rock, in which the grinding medium consists of larger pieces of rock and steel balls. Water management: The process in which the groundwater level in the mining area is lowered by pumping water from wells and the water is discharged into the groundwater system through infiltration, reinjection or irrigation recirculation and used or recharged. Probable ore: material for which tonnage and grade are calculated partly from specific measurements, samples or production data and partly from projections of reasonable distance based on geological evidence; and for which the sites available for inspection, measurement and sampling are too far away or unreasonably separated to fully define the material or consistently determine its quality. For more information, see the SEC`s Privacy and Security Policy. Thank you for your interest in the U.S. Securities and Exchange Commission. Reserves: Part of a mineral deposit that could be exploited or produced economically and legally at the time the reserve is determined. Reserves are usually expressed in relation to ore when it comes to metallic minerals. There are two categories of reserves: the ball mill: a steel cylinder loaded with steel balls into which the crushed ore is introduced. The ball mill is turned, which causes the balls to cascade and the ore to grind. Solvent extraction (SXEW): a type of heap leaching and subsequent processing of secondary copper ores in which oxidized copper minerals are dissolved. The copper-containing solution is processed to electrolytically recover the metallic copper from the solution.

By-product: secondary metal or mineral product that is recovered in the grinding process. Reverse circulation: drilling that produces rock chips rather than cores; The chips are pressed to the surface by air and collected for examination and analysis. Faster and cheaper than diamond drilling. Mill: a factory where ore is finely ground and valuable minerals are recovered through physical and chemical processes. The tunnels were used in Cornwall before 1500 and were important to the tin and copper mines of Cornwall and Devon, as the mineralized veins are almost vertical and therefore serve as intrusion channels for water. [5] Mill head grade: Metal grade of the ore mined that goes to a plant for processing. Usually lower than the reserve grade due to dilution by materials that do not contain ore. Carbon in the dough: similar to the carbon process in salmon, but first the sludge is subjected to cyanide washing in separate tanks, followed by the carbon in the dough.

The carbon in the pulp is a sequential process, while the carbon in the leaching is a simultaneous process. Mineral deposit: any unusual mineral concentration, that the valuable components can be extracted profitably (see ore and mineral body).