Types of mining: open pit, underground, placer and quarries

There are 4 main types of mining by extraction method: open pit, underground, placer (alluvial), and non-metallic mining dedicated to construction materials, each with its own equipment, depth range and environmental risks. The SGM defines a quarry (banco de materiales), in its 2023 Anuario, as an open-pit excavation for extracting stone material destined for construction.

Key facts

• Open-pit mining: surface extraction, no tunnels, in stepped terraces.
• Underground mining: tunnels and galleries to reach deep deposits.
• Placer (alluvial) mining: extraction of loose sediment in rivers, without drilling rock.
• Quarry (banco de materiales): open-pit excavation for stone material for construction (SGM 2023 glossary).
• LGEEPA Article 7, section X, gives states environmental control over rock used only in construction.

What is open-pit mining?

Open-pit mining extracts minerals directly from the surface of the land, through open excavations organized in stepped terraces or benches. It does not require tunnels: machinery reaches the material by removing the upper layers of soil and rock down to the deposit.

It is the most common method for deposits close to the surface with a large horizontal extent, such as many stone quarries — gravel, sand, limestone — and some shallow metallic deposits. It allows larger-scale equipment than underground mining, since there are no confined-space constraints.

What is underground mining, and how does it differ from open-pit mining?

Underground mining builds tunnels, galleries and access shafts to reach mineral deposits at greater depth, where removing the entire surface layer of land would be neither viable nor economical. The mineral is extracted from inside and transported to the surface through those same access points.

The main difference from open-pit mining lies in the relationship between the deposit's depth and the volume of material that would have to be removed to reach it. When that ratio is unfavorable, underground extraction, despite being more complex to engineer, becomes the viable option. It is the typical method for deep metallic deposits and some coal deposits.

What is placer or alluvial mining?

Placer mining, or alluvial mining, extracts minerals — typically gold — from loose sediment deposited by water in riverbeds, river terraces or alluvial fans. Unlike open-pit or underground mining, it does not drill into solid rock: it works on material already fragmented by natural processes.

The methods are physical: washing, screening and density separation, taking advantage of the fact that the target mineral is usually heavier than the surrounding sediment. It is one of the oldest extraction methods and, given the type of deposit it works, distinct in scale and technique from hard-rock mining.

What is a quarry, and how does it relate to non-metallic mining?

A quarry (banco de materiales) is, per the glossary of the SGM's Anuario Estadístico de la Minería Mexicana 2023, an open-pit excavation for extracting stone material for the construction industry. In method, it is a case of open-pit mining, but it is distinguished by the destination of the material: gravel, sand, stone or base for construction, not metals or industrial minerals.

Within non-metallic mining, a quarry sits alongside other non-metallic extractions — limestone for cement, fluorite, celestite, barite — but only material destined exclusively for construction falls outside the Ley Minera's concession regime, as explained in the article on what mining is and in more detail in what a quarry is and how it is regulated.

What are the advantages, drawbacks and environmental impact of each?

Open-pit mining, including quarries, has a lower extraction cost and greater operational safety than underground mining, since it does not depend on confined spaces. As a drawback, it disturbs a larger surface area and changes the landscape while the operation runs, which requires a restoration plan once the quarry is exhausted.

Underground mining affects a smaller surface area, but carries higher operational risk — ventilation, tunnel stability — and a higher extraction cost per unit of mineral. Placer mining has low impact on solid rock, but can alter riverbeds and sediment if not managed carefully.

Environmental impact does not depend only on the method, but on the mineral, the scale and the restoration that follows. For rock that can only be used in construction materials, LGEEPA, in Article 7, section X (amended January 19, 2026), gives states control over the pollution generated by its use, distinct from the federal regime that applies to concessioned mining.

How does Grupo Server help?

Triturados Gramol, a Grupo Server company founded in 2003, produces stone aggregates — gravel, sand, ballast, base and asphalt surface course — with two operating plants, in Coahuila and San Luis Potosí, stone material for construction that the Ley Minera leaves outside the concession regime. You can review its product line on the Triturados Gramol page and the rest of the group's construction operation under construction.

For questions about aggregate supply, the contact form connects directly with Grupo Server in Saltillo, Coahuila.