Mineral Resources

What is a mineral resource?

• Any [ ] of naturally occurring material in or near the Earth’s crust.– Can be extracted and processed affordably

• Nonrenewable mineral resources– Take billions of years to develop under anaerobic

conditions, extreme temperatures and pressure.

Types of Nonrenewable mineral resources

1. Metalic– Iron, copper, aluminum

2. Nonmetalic– Salt, clay, sand, phosphorus

3. Energy– Coal, oil

Categories of nonrenewable resources

• Identified– Deposits of known quality, quantity and location.

• Undiscovered– Potential supplies that are assumed to exist due to

knowledge of geologic regions

• Reserves– Identified resources where a useable nonrenewable mineral

may be mined for profit.• Majority of predictions are based off of known reserves

How do these minerals form?

• Ore formation is due to the upward movement of magma at plates. (think back to mantel plumes)

Hydrothermal process

• Divergent plates fill with magma and salt water.

• Minerals are dissolved and cool into hydrothermal ore deposits located around black smokers that lead to precipitate of Pb, Zn, Cu, Au, Ag.

Sedimentary Sorting

• Occurs with movement of water.

• Minerals are carried and separated based on size.

What do we use?• Ore: rock with enough of 1 or more metallic minerals

to be mined profitably.• Gangue: waste material from mining.• Tailings: left over material from separation of ore

from gangue

Mining and Extracting of mineral resources:

• Surface mining– Mining of shallow mineral deposits• Removal of vegetation, soil, rocks (everything above

the mineral deposit) which is referred to as overburden• This overburden is then turned into spoils or piles of

waste material.

– 90% of nonfuel + rock resources in the US– 60% of coal in US

Dredging

• Mining out of riverbeds or water sources.– Gold, sand

• Also used to channel rivers.

Open pit mining

• Dig a hole to remove ore.• Referred to as quarry– Iron, copper, gravel, sand, stone etc

Strip Mining

Done of flat terrain.• Remove overburden• Dig slit and remove

mineral.• Fill back with

overburden.• Repeat

Creates soil banks: series of highly erodible hills

Contour Strip Mining

Done on hills that are terraced to remove ore. Overburden dumpedinto terrace below.

Highwall: wall of dirt in front of erodible soil

Mountain Top Removal

Explosives used to remove overburden and reach coal or other ore.Removes entire top section of mountains.HUGE ENVIRONMENTAL IMPACT BUT SAFER FOR WORKERS

Negatives to Surface mining

1. Waste material• Mining waste accounts for ¾ of U.S. solid waste

2. Acid Mine Drainage• Water from rain that hits spoil piles carries H2SO4 to surface

water or can leach into groundwater

3. Harmful emissions released into atmosphere from smelting.• Both surface and subsurface mining, part of heating process

to remove impurities.

4. Environmental Damage and drastic impact on biodiversity.

Surface Mining Control Reclamation Act of 1977 (SMRCA)

• Requires mining companies to restore land to the original pre-mined condition to limit environmental impact of coal mining.– Created regulations for current coal mines in the

United States– Created a tax to fund the restoration of

previously abandoned mines.

Subsurface mining

• Mining of mineral resources that are located further below Earth’s surface.

• Pros:– < 1/10 land disturbed compared to surface mining

Room and Pillar

Environmental Impact of mining

1. Scarring land– ~500,000 mines in the US which cost $10s of

billions.

2. Collapse and subsidence3. Acid mine drainage– Sulfuric acid in water supplies

4. Erosion5. Toxic chemical emission into atmosphere – smelting

subsidence

Supplies of our mineral resources

• Amount depends on1. Actual (potential) supply2. Rate of usage

• Depletion time: time it takes to use up ~80% of mineral reserves at current usage rate.

• Reserve to production ratio: # of years proven reserves will last at current annual reduction costs– Best available projections

Is there enough to go around?

• Depletion time: length of time for ~80% of the mineral resource to be used.

• Minerals never truly get depleted but they become economically depleted when the cost to mine, transport and process is too costly.

Is there enough to go around?

But does the economy impact the depletion time?

• Scarce resources = increase costs– This can promote research into better mining

practices, technologies, sustainability and efficiency.

BUT…• Government has more control– Depletion allowances: deduction of costs for

developing and extracting resources from taxable income (5-22% of gross income)

– Subsidies, tariffs– No longer a true competitive free market

So is it possible to extend the length before economic depletion occurs?

• Utilize lower quality ore – Better technologies allow for ore that used to be

considered waste to now be processed.• Mine in new locations– Oceans– Shale and tar sands