Definitions
• Mineral– a solid homogenous (crystalline) chemical
element or compound; naturally occurring
• Ore– rock substance containing a valuable mineral
which is mined for that substance– ores are concentrated around the world in ore
deposits
Some minerals and their sources• Plate boundaries
– melting allows settling by density – mercury• Igneous processes
– Magma cools and crystallizes - diamonds• Sedimentary processes
– Settling by size – sand– Settling by density - gold– Evaporation – salt
• Biological processes– CaCO3
• Weathering– Water (and acid) carries minerals down and concentrates them -
copper• Minerals from the sea
– Sulfur (vents) and manganese nodules
Methods of Mining
• Subsurface mining– coal mining
– disturbs less than 1/10 as much land
– produces less waste
– more dangerous
Methods of Mining• Surface mining
– open-pit mining• copper, iron, sand, gravel, limestone
– dredging• buckets and draglines scrape underwater deposits
Strip mining• overburden (and all vegetation) is removed in strips• resource is removed• spoil is replaced in rows• spoil is susceptible to erosion (sediment pollution)• rainwater leaches chemicals into ground water (acid
drainage)
Mine tailings• Mine tailings often include sulfide
compounds• When these react with water, sulfuric acid
and toxic minerals can be washed into local water
Processing Materials
• Minerals are extracted from ores by heating or chemical reactions– smelting - roasting the ore - produces huge
amount of air pollution (SOx)
Heap-leach Extraction
• heap-leach extraction - separating gold from low grade ores - spraying rock with a cyanide solution which dissolves the gold - mining sites are often left unaltered with high toxin levels
Placer Mining• placer mining
– Destroys riverbanks– Increases sediment in rivers– Uses heavy metals like Mercury that contaminate
waters• in the Amazon, gold miners are using mercury and have
dumped 100 tons of mercury into the Amazon river
Classification of resources and reservesA reserve is is that portion of a resource that is identified and from which usable materials can be legally and economically extracted at the time of evaluation
Resources are not reserves