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  1. Hydrothermal ore deposits are minerals that are formed from hot, mineral-rich fluids that circulate through the Earth's crust. These fluids, which are a mixture of water and various dissolved minerals, are heated by magma and other geological processes, and are then expelled from the Earth's interioRead more

    Hydrothermal ore deposits are minerals that are formed from hot, mineral-rich fluids that circulate through the Earth’s crust. These fluids, which are a mixture of water and various dissolved minerals, are heated by magma and other geological processes, and are then expelled from the Earth’s interior through vents in the crust.

    When these hot fluids come into contact with cooler rocks and minerals, they can deposit minerals such as sulfides, oxides, and silicates in the surrounding rocks. Over time, these mineral deposits can become concentrated and form ore deposits, which can be mined for valuable minerals such as copper, gold, silver, and zinc.

    The formation of hydrothermal ore deposits is an important process in the formation of many types of mineral deposits, including porphyry copper deposits, epithermal gold deposits, and volcanic-hosted massive sulfide deposits. These deposits can have a significant impact on the economies of the regions where they are found, and can provide important resources for various industries, including mining, metal production, and electronics.

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  2. This answer was edited.

    All the common ore-forming elements are present in magmas and ordinary rocks, in amounts ranging from a few parts per billion to several thousands of parts per million. Selective concentration of one or more ore constituents to form a mineral deposit is achieved by some combination of the following:Read more

    All the common ore-forming elements are present in magmas and ordinary

    rocks, in amounts ranging from a few parts per billion to several thousands of

    parts per million. Selective concentration of one or more ore constituents to

    form a mineral deposit is achieved by some combination of the following:

    1. extraction of the constituents from magmas, rocks, and oceans;
    2. transport of the constituents in a fluid medium from the source region to the site of deposition.
    3. localization of the constituents at certain favorable sites.

    The ore-forming processes may be grouped into the following four broad

    categories:

    1. Orthomagmatic processes
    2. Sedimentary processes
    3. Metamorphic processes
    4. Hydrothermal processes
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  3. ⚫Auger Mining 🔷Auger mining means a method of mining coal at a cliff or highwall by drilling holes into an exposed coal seam from the highwall and transporting the coal along an auger bit to the surface and includes all other methods of mining in which coal is extracted from beneath the overburden bRead more

    ⚫Auger Mining

    🔷Auger mining means a method of mining coal at a cliff or highwall by drilling holes into an exposed coal seam from the highwall and transporting the coal along an auger bit to the surface and includes all other methods of mining in which coal is extracted from beneath the overburden by mechanical devices located at the face of the cliff or highwall and extending laterally into the coal seam, such as extended depth, secondary recovery systems

    As the auger rotates and advances forward, coal is cut and pushed out of the hole by the rotating action of the auger.

    🔹The action is similar to that of a carpenter boring a large hole in wood using an auger bit, and that is where the name derives.

    🔷Auger mining recovers around one-third of the coal under the highwall, for whatever depth of penetration is achieved.

    🔹 Auger cutting heads can be as large as 7 feet in diameter and may be drilled to a depth of more than 300 feet.

    When the ultimate pit limit is reached, it is difficult to “pack up and leave” when you see the exposed coal seam.

    🔹 So, in some regard, the company looks at this secondary recovery technique, i.e., auger mining, as the “icing on the cake.

    🔹” It amounts to coal recovery at a very low cost. It is, however, somewhat problematic and controversial.

    🔷The low recovery, less than 35%, means that the majority of the reserve remains in place, but it has been sterilized, i.e., left in a condition where it will be essentially impossible for anyone to recover the remainder in the future.

    🔹The holes into the side of the hill create drainage holes for acid-laden water, and that is a big problem.

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  4. ⚒ Room-and-pillar mining ◽️In this method, a number of parallel entries are driven into the coal seam. The entries are connected at intervals by wider entries, called rooms that are cut through the seam at right angles to the entries ◽️ The resulting grid formation creates thick pillars of coal thatRead more

    ⚒ Room-and-pillar mining

    ◽️In this method, a number of parallel entries are driven into the coal seam. The entries are connected at intervals by wider entries, called rooms that are cut through the seam at right angles to the entries

    ◽️ The resulting grid formation creates thick pillars of coal that support the overhead strata of earth and rock.
    ⚫️ There are two main room-and-pillar systems,
    ▪️the conventional
    ▪️ the continuous.

    ◽️In the conventional system, the unit operations of undercutting, drilling, blasting, and loading are performed by separate machines and work crews.

    ◽️In a continuous operation, one machine—the continuous miner—rips coal from the face and loads it directly into a hauling unit.

    ➡️ In both methods, the exposed roof is supported after loading, usually by rock bolts.

    ◽️Under favorable conditions, between 30 and 50 percent of the coal in an area can be recovered during the development of the pillars. For recovering coal from the pillars themselves, many methods are practiced, depending on the roof and floor conditions.

    ◽️The increased pressure created by pillar removal must be transferred in an orderly manner to the remaining pillars so that there is no excessive accumulation of stress on them. Otherwise, the unrecovered pillars may start to fail. endangering the miners and mining equipment. The general procedure is to extract one row of pillars at a time, leaving the mined-out portion, or gob, free to subside. While extraction of all the coal in a pillar is a desirable objective, partial pillar extraction schemes are more common.

    ◽️At depths greater than 400 to 500 meters, room-and-pillar methods become very difficult to practice, owing to excessive roof pressure and the larger pillar sizes that are required.

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