There are two types of mining: surface and underground. Surface mining is much more common than underground mining.
There are also two main types of ore deposits that are mined both by open pit and underground methods:
Placer deposits. Placer deposits are found in rivers and streams, as well as in beach sands.
Lode deposits. Rock deposits are contained in rock bodies through layers, veins, or mineral grains.
Surface mining
Mining activities are carried out on the surface of the earth. Overburden will be removed to expose the ore body below.
Surface mining methods include:
- Strip mining. Strip mining uses dragline excavators to remove overburden from the ground surface and expose the ore body. Strip mining is also used to prepare land for open pit mining, quarrying, and mining.
- Open-pit mining is the development of mineral resources. Open-pit mining is a technique that involves drilling into the earth’s surface to place explosives. The explosions expose the underlying rock and create large pits from which miners can extract ore. This surface mining technique can be used to extract silver.
- Open pit mining. Quarrying, another form of surface mining, is used to extract slabs and byproducts of marble, granite, and other hard stones.
- Mountaintop removal mining. Mountaintop removal mining is used primarily in the Appalachian Mountains for coal mining. The mountaintop will be cleared into the adjacent valleys, and the top 300 meters will be blasted to open up the coal seams in the quarry.
- Highwall mining. High-wall mining is used to extract the remaining coal from the seam using a continuous shaft. It is used in combination with strip mining and open pit mining and is used to target coal seams from the sides when there is a thick overburden layer on top of the seam.
- Placer mining. A combination of water and tanks is used to extract gold and other precious metals that are found in sand and gravel. These precious metals have a higher density than water and sink faster than surrounding materials.
- In-situ leaching (ISL) mining. In-situ mining is a somewhat unconventional mining method that uses neither surface nor underground mining methods. Instead, valuable materials are dissolved in situ with water, carbonate solutions or acid without removing the surrounding rock.