Surface mining involves the extraction of minerals and resources from the Earth near its surface, without the need for tunnelling deep underground. There are several main approaches used in surface mining, each designed to access different types of deposits and terrain.
Open-Pit Mining
Open pit mining, also known as open-cast mining, is a surface mining method used to extract unconsolidated materials such as minerals, stone, sand, and gravel from deposits located near the earth’s surface. Before mining begins, extensive geological surveys and testing are carried out to determine the depth, volume, and composition of the deposit.
Once it is confirmed that mining the deposit is economically feasible, the top layer of soil and vegetation, known as the overburden, is removed to expose the targeted material. A deep pit with steep, sloping sides is then systematically designed and engineered to allow excavation machinery to access and extract the deposit. This material is then transported to a nearby processing facility, often located on the same site.
In sand and gravel pits, for example, front-end loaders are commonly used to extract material from the base of the pit wall. The material is then loaded into haul trucks or directly onto belt conveyors, which carry it to the processing plant over longer distances.
At the processing facility, the material is typically washed, crushed, sorted, and separated into different size categories, with each size stockpiled separately. In many cases, a cement plant is also located on-site, where sand and gravel are mixed according to specific requirements to produce concrete. This concrete is then delivered to nearby construction sites as needed.
Quarry Mining
Quarry mining shares many similarities with open-pit mining, but the key distinctions lie in the type of material extracted and the mining techniques employed. While open pits typically target loose or unconsolidated materials like sand and gravel, quarries are designed to extract consolidated rock, often referred to as dimension stone, such as granite, marble, and limestone.
Unlike open pits with gently sloping walls, quarries usually feature vertical or near-vertical walls of solid rock. To extract large stone blocks, quarry operations often rely on drilling, blasting, and cutting methods. Many of these techniques, apart from modern tools like diamond-bladed saws, have remained fundamentally the same for thousands of years. However, today’s operations are aided by powerful cranes and derricks, which lift and transport the extracted blocks to nearby processing facilities.
Once at the processing site, the massive stone blocks are further cut into smaller pieces or slabs and then polished to fine finishes. These finished products are commonly used for kitchen countertops, commercial building façades, monuments, and cemetery headstones.
In addition, leftover stone fragments and remnants are often crushed into specific sizes for use in various construction materials or ground into powder for use in numerous industrial and food-grade applications.
Strip Mining
Strip mining is a surface mining method used to extract seams of material, most commonly coal and lignite, that lie relatively close to the earth’s surface. Similar to open-pit mining, this method begins with extensive exploration and economic evaluation to determine the feasibility of extraction.
In large-scale operations, the overburden (the material covering the seam) may first be loosened through blasting. Once dislodged, the overburden is removed using draglines or front-end loaders to expose the underlying coal.
With the seam exposed, powerful excavation equipment, such as power shovels equipped with massive buckets, is used to extract the coal. The coal is then loaded onto large haul trucks or moved via overland conveyors to preparation plants for further processing.
This method of continuously removing overburden and extracting material along benches above the seam is repeated until the coal seam is completely mined out.
After extraction is complete, the site enters a reclamation phase. This involves backfilling the excavated area with overburden, grading the land to its original or improved contour, and replanting vegetation to restore the environment.
