Mining and Ore Processing: Comprehensive Study Notes

MINING

  • Involves withdrawing useful resources from non-renewable stocks. Specifically refers to the extraction of mineral resources. Essential due to the inability to grow certain materials.

ORES

  • Naturally-occurring materials that can be profitably mined, including minerals and rocks.

  • A deposit is considered a potential ore body if its localized abundance exceeds the average distribution in Earth's crust.

  • Ore bodies are unevenly distributed and located through sophisticated geologic processes.

  • All ores are minerals, while all minerals are not ores, since some minerals may contain large amounts of unwanted substances such as sand, stones, and earthly impurities.

  • Example: Aluminium occurs in the Earth's crust in the form of two minerals: bauxite and clay.

  • ORES TREASURES BENEATH OUR LAND (regional highlights):

    • LUZON (Metro Manila): Quantity of mineral resources per unit area; 3rd in the world for gold; 4th in the world for copper; 5th in the world for nickel; 6th in the world for chromite.

    • MINDANAO: Gold, Copper; Chromite, Nickel; Magnetite; Manganese.

    • VISAYAS: Davao (regional notes on mineral presence).

EXPLORATION

  • Methods in Finding Ore:

    • Gravimetric

    • Self-Potential

    • Induced Polarization

    • Exploratory Drilling

GRAVIMETRIC

  • SPECIFIC GRAVITY COLLECTION

    • Higher specific gravity rocks often indicate valuable ores; geologists map gravimetric values to predict ore locations.

    • Darker ore bodies cause higher gravity readings due to higher density relative to surrounding rock.

METALLURGY

  • Definition: Extracting metals from ores and modifying them for use.

  • Focuses on commercial methods rather than laboratory methods.

  • Involves chemical, physical, and atomic properties of metals and alloy formation principles.

  • STEPS OF MINING AND MINERAL PROCESSING
    1) EXPLORATION: locating, mapping, and sampling the ore body.
    2) MINING: extracting the ore by drilling and blasting, removal of waste, and hauling.
    3) MILLING: crushing and grinding the ore.
    4) CONCENTRATING: removing ore from waste rock and freeing the target mineral from its surroundings.
    5) TRANSPORTATION to the refinery by rail, ship, or truck. The refinery may be nearby or far away.
    6) SMELTING: chemically separating the target metal, usually through heating.
    7) REFINING: using electrolysis to purify the target metal to
    +99.9% purity.

  • Mine Site vs Refinery

    • A refinery is often located at or near the smelter site.

SELF-POTENTIAL (SP) AND INDUCED POLARIZATION (IP)

  • SELF-POTENTIAL (SP)

    • Ground water can act on metals in a deposit to produce a weak electric charge (like a huge but weak battery).

    • Measuring surface voltages can show significant changes when mineralization is present beneath the surface.

    • The ore body generates a current through surrounding rocks; this current can be detected at the surface.

  • INDUCED POLARIZATION (IP)

    • By measuring the voltage caused by the electric field with a second pair of electrodes at a distance, resistivity of the ground can be calculated.

    • If even small amounts of metallic minerals are present, the ground can become charged by the electric field, producing induced polarization.

    • Process: ground is electrified by two electrodes placed a distance apart; current flows through the ore body, which holds the charge briefly.

EXPLORATORY DRILLING

  • The final proof of mineralization—short of actual mining—is drilling.

  • A series of cores are taken at set intervals over a known anomaly and analyzed for mineral content.

  • The all-important grade (ratio of recoverable metal to waste rock) is established primarily through this exercise.

  • From a single drill site, a core is drilled in several different directions to assess mineral presence.

  • Drills bring up core cylinders of rock that can be analyzed.

IN-SITU MINING (SOLUTION MINING)

  • Also referred to as solution mining.

  • Does not involve removing intact ore from beneath the earth's surface.

  • Involves pumping chemicals underground to dissolve ore, then pumping the resulting "pregnant solution" back up to the surface for processing to recover minerals.

  • Mainly used in uranium mining.

  • Simple schematic elements:

    • Mining solution from processing plant

    • Submersible pump and injection well

    • Recovery well

    • Sands, clays, and gravels with uranium-bearing sand/clay layers

    • Uranium solution sent to processing plant

  • SURFACE MINING

    • Involves removal of plant life, soil, and potentially bedrock to access resource deposits.

    • Normally used for fairly shallow, non-precious deposits.

    • Two foremost kinds: Open-pit mining and Strip mining.

PLACER MINING

  • Placers are unconsolidated deposits formed by weathering via water and/or wind action.

  • Typically found in riverbeds, sands, or other sedimentary environments; involves sifting valuable materials from sediments.

  • Common activities include panning for gold and sluicing.

  • Dredging is an advanced form of gold panning, using floating dredges with conveyors and scoops to extract minerals from water tables.

  • Extracted minerals include gold, tin, aluminum, mineral sands, diamonds, rock salts, sand, and gravel.

MILLING AND SURFACE MINING NOTES

  • Underground mining is mostly used for lead and zinc;

  • Surface mining is mostly used for coal and copper.

  • Ore is ground and crushed using jaw crushers and cone crushers to achieve a gravel-like consistency.

  • Water is added to the ore in ball or rod mills, creating a fine slurry.

STRIP MINING

  • Strip mining strips away the surface from the mineral seam (usually coal).

  • Soil, rock, and vegetation over the mineral seam are removed with large machines (bucket-wheel excavators).

  • Mostly used to extract shallow, “bedded” deposits where a mineral layer is covered by soft topsoil and weathered rocks.

  • Area stripping moves ore over large flat terrains in long strips; overburden from one strip is dropped into the previous strip to avoid leaving large gaps.

  • Contour mining follows the contours of outcrops and hilly terrains, mining along the seam with smaller, customized excavations.

OPEN-PIT (OPEN-CUT) MINING

  • Involves digging out rocks to form an open pit or borrow pit from which ore is extracted.

  • Generally features stepped sides to minimize collapse risk and a large ramp for mining equipment.

  • Quarries produce building materials and dimensional stone.

  • Open-cast mines typically have benches for vertical levels (usually four to sixty meters apart); many smaller quarries lack benches.

  • Environmental note: tailings are the processed ore slurry stored in dams or ponds; can contain harmful substances like sulfide minerals and cyanide, posing environmental risks.

CONCENTRATING OF ORES

  • Methods include hydraulic washing, magnetic separation, froth flotation, and leaching.

a) HYDRAULIC WASHING

  • Concentrates ore by passing it through an upward stream of water; lighter gangue minerals are separated from heavier metal ore (gravity separation).

  • Key components: fine ore particles, water current, gangue, Wilfley table, separated ore.

b) MAGNETIC SEPARATION

  • Uses magnetic properties to separate ore from gangue.

  • Process: ore is ground into fine pieces and passed over a conveyor belt with a magnetic roller; magnetic ore sticks to the belt while non-magnetic gangue falls off.

  • Diagrammatic concept: finely ground ore, non-magnetic particles, magnetic particles, magnetic roller.

c) FROTH FLOTATION

  • Primarily used to remove gangue from sulfide ores.

  • Ore is powdered and suspended in water with collectors and froth stabilizers.

  • Collectors (e.g., pine oils, fatty acids) increase non-wettability of the metal portion, enabling froth formation and separation.

  • Visual schematic: flotation cell with air supply, froth concentrate, tailings, slurries, and bubbles.

d) LEACHING

  • Used when ore is soluble in a solvent.

  • The powdered ore is dissolved in a chemical solution (commonly a strong NaOH solution);

    • The metal in the ore dissolves in the chemical solution and can be extracted and separated from the gangue by processing the chemical solution.

  • Process flow: ore heap → chemical recovery plant → pregnant pond → preparation → solution collection.

ORE FOR HUMAN USE

  • Commonly exploited ores include aluminum, gold, iron, nickel, platinum, zinc, etc.

  • Additional mentions (illustrative): lead, barite, silica, cadmium, limestone, talc.

BENEFITS OF MINING IN THE PHILIPPINES

  • Provides significant employment opportunities.

  • Spurs local and regional economic development through investments in infrastructure and utilities.

  • Contributed ₱25.52 billion from taxes, fees, and royalties.

  • Generated 184,000 jobs.

  • Committed ₱25.71 billion for the Social Development Management Program (SDMP).

SMELTING

  • Smelting is a form of extractive metallurgy to produce a metal from its ore.

  • It uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal behind.

REFINING

  • The refinery is usually located at the same site as the smelter.

  • Refining typically involves electrolytic refining: the impure metal from the smelter is placed in an electrolytic solution and connected to a voltage source to purify the metal to high purity.

DESTRUCTION OF LAND AND ENVIRONMENTAL IMPACTS

  • Mining causes loss of land due to chemical contamination and destruction of soil layers.

  • Large operations disturb land by removing material and dumping waste; significant wildlife habitat loss can occur.

  • NOISE: Blasting and transport cause noise disturbances to local residents and wildlife; studies show bluebirds have fewer chicks due to noise pollution; noise hinders animals’ ability to navigate, find food, mate, and avoid predators.

POLLUTION AND ENVIRONMENTAL RISKS

  • Mining pollutes the atmosphere, surface waters, and groundwater.

  • Rainwater seeping through spoil heaps can become contaminated, acidic, or turbid, with devastating effects on nearby streams and rivers.

IMPACT ON THE BIOLOGICAL ENVIRONMENT

  • DIRECT IMPACTS: Death of plants or animals caused by mining activity or contact with toxic soil or water from mines.

  • INDIRECT IMPACTS: Changes in nutrient cycling, species diversity, and ecosystem stability due to alterations in groundwater or surface water availability and quality.

NOTES AND CONNECTIONS

  • The material integrates exploration, extraction, processing, and environmental considerations.

  • Real-world relevance: technology (IP, SP, drilling), processing choices (concentration methods), and environmental safeguards influence mine feasibility and sustainability.

  • Foundational principles: density-based prospecting, mineral beneficiation, energy-intensive processing, and ecological stewardship.

  • Ethical/philosophical implications: balancing resource extraction with habitat protection, pollution control, and long-term ecological health.

ext{Grade} = rac{ ext{recoverable metal}}{ ext{waste rock}}