Transcript MINING
MINING • Mineral Resource: Naturally occurring material in or on Earth’s crust that can be extracted and processed into useful materials for a profit. • Ore: a rock containing enough of one or more metallic minerals that can be mined profitably. • Reserves: easily extracted and economical to mine. Example: Gold Ore Example: Iron Ore (steel!) Iron Ore Outcrop Uranium Ore Copper Ore • Overburden: the material above the mineral in survface mining that has to be moved before mining commences. Gangue: commercially valueless material Tailings: the leftovers when the gangue is removed from the ore • Tailings ponds/slurry = toxic! Spoils: any waste from mining Environmental Effects: • AMD: highly acidic water rich in heavy metals – water+rocks that contain sulfur = sulfuric acid – Heavy metals can be leached from rocks that come in contact with the sulfuric acid • Treatment: most often liming: lime neutralization; when the pH becomes neutral, heavy metals such as iron precipitate (“yellow boy”) • Acid Mine Drainage Smelting: separating metal from gangue or other elements in the ore • Heat and chemical reactions – melt the metal but release air pollutants and leave “slag”. Gold Extraction using Cyanide Cyanide Heap Leaching (Au) TYPES OF MINING Surface and Subsurface Surface Mining • Open Pit • Dredging • Strip Mining • Mountain-top Removal Subsurface Mining • Room and Pillar • Longwall In-Situ Depletion of mineral resources: • Depletion curve – Throw away – Recycle – Reduce, reuse Legislation • Mining Law of 1872: Encouraged the mineral exploration and mining of hardrock minerals on U.S. public land. • Surface Mining Control and Reclamation Act (SMCRA): (1977) requires any surface mining be “reclaimed”. This means that soil surface must be “restored” to its original condition.