lecture 18: metal production

open pit mine example

Mir diamond mine Russia

Mir diamond mine facts

• Hole depth: 525 m

• Upper diameter: 1100-1200 m

• Lower diameter: 160-310 m

• Mining depth: 1235 m

• Rock removed: 168.7 million cubic metres

• Diamonds: $17.5 billion

strip mining

iron ore strip mining in western Australia: vast scale, rehabilitation often impractical

underground mining

usually for higher value metals

examples of underground mines

Tara Mines, Navan; zinc and lead mining

why is most mined rock waste

re-bury it, or landscape and vegetate spoil heaps

sequence of processes

1. Crushing and grinding

2. Separation, e.g. froth flotation, electrical

3. Drying

production of tailings

wasted material, usual as a slurry that dries

smelting

treatment of ore concentrates to extract metals - high energy requirement

grade

the proportion of a rock that is made of the material of economic value

resources

some confidence than material of economic value is present in certain amount, at certain grade

reserves

high confidence that mining would be profitable - consider geological/geotechnical and sociopolitical factors

will reserves be exhausted

ore deposits still to be found can be extrapolated from known deposits using geological knowledge

copper reserves

deposits in the top 3 Km of the Earth's crust are sufficient for 5500 years at present rate of use

reserves are dynamic

• scarce metal - price rises

• Higher price converts some resources into reserves

• Higher price and larger reserves - more mining

• Supply increases - metal price falls

cause of price variation

1. Economic activity: spreading industrialisation, growth and recession

2. Population growth

3. New uses and discontinued uses

4. Ability to extract metals

5. Recycling

6. Energy costs

7. Socio-enviro-political: wages, taxes, wars, environmental legislation, social licence to operate

recycling of metals

energy required, technical difficulty and overall cost compared to mining

top copper producer 2005

Chile

platinum top producer 2005

South Africa

generator magnets of wind turbines

400kg Nd and 80kg Dy

by 2030 recycling of wind turbines

could supply 9% of Nd, and 7% of Dy demand

the future of metal mining

near-surface ore deposits becoming harder to find - extension of open pits to deeper levels: sublevel caving

production of metals as by-products

provides potential efficiency gains - often these metals were/are not (yet) economically or technologically extractable or seen as ‘penalty’ elements