Planned Open-Pit Mine Stirs Environmental Fight

A proposed open-pit copper and gold mine in southwestern Alaska has sparked outrage among some locals, the nearby fishing industry and a coalition of environmentalists, who worry it would carve up the pristine wilderness and poison a large salmon run.

The mine would sit on a lonely spot of tundra near Lake Iliamna, 1,000 square miles of pure freshwater ringed by a handful of native villages, including Nondalton and Iliamna.

The mining company, Canadian-based Northern Dynasty Minerals, is hoping its proposed Pebble Mine will prove to be the richest of its kind in the world, with billions of dollars in copper and gold just waiting to be dug up. It could be perfectly timed for the industrial boom in China.

Open-pit mining

The term is used to differentiate this form of mining from extractive methods that require tunneling into the earth. Open-pit mines are used when deposits of commercially useful minerals or rock are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling (as would be the case for sand, cinder, and gravel). For minerals that occur deep below the surface—where the overburden is thick or the mineral occurs as veins in hard rock— underground mining methods extract the valued material.

Open-pit mines that produce building materials and dimension stone are commonly referred to as quarries. People are unlikely to make a distinction between an open-pit mine and other types of open-cast mines,[citation needed] such as quarries, borrows, placers, and strip mines.

Medoro in Colombia

MARMATO PROJECT - COLOMBIA

With the consolidation of the Zona Alta, Zona Baja and Echandia properties, Medoro is now in a position to explore, develop and, subject to feasibility and permitting, mine the deposit as a whole. The ability to explore and drill the structure from all three license areas, including from underground, significantly improves the potential to increase and upgrade the gold resources at the Marmato Project in a relatively short time.

Medoro has acquired a significant portion of the prolific Marmato gold district in Colombia. The Marmato Project covers 1,198 hectares in the mid-Cauca gold belt in the Western Cordillera, 120 km south of Medellín in Caldas state.

Qué es la minería a cielo abierto?

Se llama minas a cielo abierto, y también minas a tajo abierto, a las explotaciones mineras que se desarrollan en la superficie del terreno, a diferencia de las subterráneas, que se desarrollan bajo la superficie.

Para ello, a veces es necesario excavar, con medios mecánicos o con explosivos, los terrenos que recubren o rodean la formación geológica que forma el yacimiento. Estos materiales se denominan, genéricamente, estéril, mientras que a la formación a explotar se le llama mineral.

Las minas a cielo abierto son económicamente rentables cuando los yacimientos afloran en superficie.