EAES FINAL MINING

Three types of minerals/rocks mined

1) Metals - ex lead, gold, copper

2) Non-metals - ex, calcite, salt, quartz

3) Aggregate - gravel, sand

Sulfide Minerals

Contain metal + sulfur

• Chalcopyrite – source of copper (Cu)

• Galena – source of lead (Pb)

often form in hydrothermal environments

Oxide Minerals

Contain metal + oxygen

• Hematite – source of iron (Fe)

• Tantalite – source of tantalum (Ta)

often form under oxidizing conditions

Ore

rock that contains naturally concentrated minerals of interest that can be economically extracted.

Gangue

the part of the rock that has no economic value at current prices and must be removed to access the ore

Disseminated

The valuable minerals are spread out diffusely through the rock, rather than clustered in veins.

• Common in low-grade ore bodies.

• Often mined via open-pit mining.

Concentrated

The minerals are clustered in high amounts in specific areas (like veins).

• Common in high-grade deposits.

• Typically mined using underground mining.

Open-Pit Mining

• Strip the land surface and dig a large hole to access shallow, disseminated, or low-grade deposits.

Open-Pit Mining- Types of Deposits:

• Shallow (<300 m), diffuse or spread-out ore bodies.

Open-Pit Mining- Advantage/Disadvantage

Advantages:

• Cost-effective for large-scale, low-grade operations.

• Easier access to ore bodies.

Disadvantages:

• Massive land disturbance.

• Requires removal of huge amounts of overburden and waste rock.

Open-Pit Mining- Environmental Impacts:

• Habitat destruction

• Erosion and sedimentation

• Large waste rock piles and potential for acid rock drainage

Strip Mining

Remove horizontal layers of soil and rock to access ore (often coal or oil sands).

Strip Mining Types of Deposits:

Horizontally-layered deposits near the surface.

Strip Mining- Advantages/Disadvantages

Advantages:

• Efficient for extracting flat-lying resources.

Disadvantages:

• Destruction of large surface areas.

• Not useful for deep or irregular ore bodies.

Strip Mining- Environmental Impacts:

• Massive surface disruption

• Loss of vegetation and topsoil

• Water contamination from runoff

Underground Mining

Principle:

• Dig tunnels into the earth to reach deep, concentrated (vein-type) ore bodies.

Types of Deposits:

• High-grade, narrow veins at depth (>300 m).

Advantages:

• Minimizes surface disturbance

• More targeted extraction of high-value ore

Disadvantages:

• Very expensive and dangerous (risk of collapse, gas exposure)

• Lower production rates compared to open-pit

Environmental Impacts:

• Less surface impact but can cause subsurface instability

• Still produces waste rock and tailings

• High energy use

Placer Mining

Principle:

• Collect loose surface sediments from riverbeds or beaches where minerals have accumulated naturally due to erosion and deposition.

Types of Deposits:

• Surface-exposed or weathered placer deposits (e.g., gold, coltan).

Advantages:

• Requires less equipment.

• Smaller footprint than open-pit mining.

Disadvantages:

• Often done by artisanal miners using simple tools—can be inefficient.

• May use toxic chemicals (e.g., mercury).

Environmental Impacts:

• Disturbs riverbanks and aquatic ecosystems

• Can lead to sedimentation and mercury pollution

Solution (In-Situ Recovery) Mining

Principle:

• Pump a leaching solution into permeable ore zones to dissolve the target minerals (e.g., uranium, copper), then pump it back out for processing.

Types of Deposits:

• Deep or thin ore bodies in permeable rock.

Advantages:

• Minimal surface disturbance

• No need for excavation or blasting

Disadvantages:

• Risk of groundwater contamination

• Requires precise control of fluids underground

Environmental Impacts:

• Contamination of aquifers if not managed properly

• Residual brine waste must be carefully disposed of

Milling

• Purpose: Crush the ore to a small, consistent particle size.

• Why?: Prepares the rock for further separation and processing.

Concentrating

• Purpose: Physically separate valuable minerals from the rest using differences in:

  • Density

  • Magnetic properties

  • Ability to attach to “frothing agents” (froth flotation)

Smelting

• Purpose: Heat minerals to high temperatures to melt and separate the metal of interest.

• Involves chemical changes and produces a solid byproduct called slag.

Refining

• Purpose: Use chemical extraction techniques to obtain the purest metal form.

• Example: Cyanide is used to dissolve gold; other chemicals are used depending on the element.

Tailings

• Fine-grained crushed rock mixed with water.

• Remains after valuable minerals are extracted.

• Stored in tailings ponds, which must be monitored and lined.

Slag

Solid byproduct of the smelting process.

acid mine drainage.

acidic, metal-rich runoff

Sulfide minerals oxidize which produces:

• Sulfuric acid (acidifies the water)

• Iron and other heavy metals (which dissolve into the acidic water)

Remediation by Physical Isolation

• Goal: Prevent oxygen and water from coming into contact with sulfide-rich waste rock or tailings.

• Methods:

  • Covering waste with impermeable linings (synthetic or natural)

  • Capping tailings piles with soil or clay

  • Double ditch systems to control water runoff