Open-pit mining

The El Chino mine located near Silver City, New Mexico is an open-pit copper mine

Open-pit mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow. 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). Where minerals occur deep below the surface—where the overburden is thick or the mineral occurs as veins in hard rock— underground mining methods are used to extract the valued material. Open-pit mines are typically enlarged until the mineral reserve is exhausted.

Open-pit mines that produce building materials are commonly referred to as quarries. People in some English-speaking countries are not likely to make a distinction between an open-pit mine and other types of open-cast mines, such as quarries, borrows, placers, and strip mines.

When they are no longer productive for extraction of material, open-pit mines are sometimes converted to landfills for disposal of solid wastes. However, some form of water control is usually required to keep the mine pit from becoming a lake.

File:Quarry8093.JPG

A coquina quarry

Materials typically extracted from open-pit mines include:

• Clay
• Coal
• Coquina
• Gravel and stone (stone refers to bedrock, while gravel is unconsolidated material, as found in glacial or fluvial deposits)
• Granite
• Gritstone
• Gypsum
• Limestone
• Marble
• Metal ores: such as copper, iron, gold, and molybdenum
• Sand
• Sandstone

Open-pit mines

This list includes only those large open-pit mines for which an article exists in Wikipedia.

• Adams Mine – controversial abandoned mine in Kirkland Lake, Ontario.
• Chuquicamata – Chilean copper mine
• Kennecott Copper Mine – copper mine in Salt Lake County, Utah, United States; largest open-pit mine in the world
• El Chino mine – copper mine in Grant County, New Mexico, United States
• Lavender Pit – copper mine in Cochise County, Arizona, United States.
• Berkeley Pit - former copper mine in Butte, Montana, United States; now a toxic lake.
• Ekati Diamond Mine – diamond mine in Northwest Territories, Canada.
• Diavik Diamond Mine – diamond mine in Northwest Territories, Canada.
• The Big Hole, a diamond mine in Kimberley, South Africa that reaches a depth of more than 1,000 meters.
• Colomac Mine – gold mine in Northwest Territories, Canada.
• Pine Point Mine – lead and zinc mine in Northwest Territories, Canada.
• Udachnaya pipe – diamond mine in Yakutia, Russia.

See also

• List of minerals
• List of stone