Mining: factors and methods

Detail

What mining is, and how it grew

• Mining means taking useful minerals out of the earth's crust. A mineral is a natural, non-living substance with a fixed chemical make-up.
• Whole stages of human history are named after minerals:

• Copper Age, then the Bronze Age (bronze is copper mixed with tin), then the Iron Age.

• In ancient times, minerals had only a few uses. People used them for tools, utensils (pots) and weapons.

• Real, large-scale mining began with the Industrial Revolution (from the late 18th century). Factories, railways and steam engines needed huge amounts of coal and iron. Since then, the importance of mining has kept growing.
• Link: which rocks hold which minerals (metallic ores in igneous and metamorphic rocks; coal, petroleum and salts in sedimentary rocks) is covered in minerals-rocks-rock-cycle.

Factors affecting mining activity

Whether a mine makes a profit depends on two groups of factors.

Group	Factor	What it means
Physical	Size of the deposit	A large deposit can be mined for many years, so the cost of setting up the mine is spread out.
	Grade of the ore	Grade means how much metal is in the rock. High-grade ore gives more metal for each tonne dug.
	Mode of occurrence	Where and how the mineral lies: near the surface or deep down, in thick beds or thin veins. This decides the mining method and its cost.
Economic	Demand	High demand and high prices make mining worth it.
	Technology	Better machines make it possible to reach deeper ores or ores that are harder to treat.
	Capital	Money is needed for infrastructure (roads, railways, power, water) and for machines.
	Labour and transport costs	Cheap labour and cheap transport to markets or ports lower the total cost.

• Key idea: a deposit is "workable" only in economic terms.
• A low-grade deposit may be left alone today.
• If prices rise or technology improves, the same deposit can start making a profit.
• So the mineral map of the world keeps changing over time, even though the rocks do not.

Methods of mining (NCERT Fig. 4.19)

The method depends on the mode of occurrence and the nature of the ore.

Surface or open-cast mining

• Open-cast mining means digging minerals that lie close to the surface.
• Process:
• The overburden (the layer of soil and rock that covers the mineral) is removed first.

• The mineral bed is then dug out from a wide, open pit, usually with large shovels, dumpers and draglines.

• Advantages:

• It is the easiest and cheapest method.
• Safety precautions and equipment cost little, compared with underground mines.

• Output is large and quick.

• Problems:

• It scars the land, leaving big pits and dumps of waste rock.
• It displaces people, because villages, farms and forests over the deposit must be cleared.

• The land needs reclamation (bringing mined land back to use by filling pits, making slopes stable and planting trees).

• India: open-cast mining is now the main method for coal.

• The share of underground mining in India's coal output fell every year: 5.54% (2019-20) → 4.50% (2020-21) → 4.26% (2021-22) → 3.90% (2022-23) → 3.44% (2023-24) [7].
• So about 96–97% of Indian coal (2023-24) comes from open-cast mines [7].
• Mine closure means closing and securing a mine once mining ends. Its closure plan restores the land by filling open pits, making slopes stable, managing waste dumps and planting trees. Afforestation is the main part of this work [8].
• Coal companies have found 179 pre-2009 and 162 post-2009 abandoned or discontinued mines. Of these, 147 are marked for closure. The rest are being joined to working mines and started again [8].
• For coalfields in India, see mineral-resources-india.

Underground or shaft mining

• Underground mining is used when the ore lies deep below the surface.
• Process:
• Vertical shafts (deep, straight holes) are sunk into the ground.
• Underground galleries (horizontal tunnels) branch out from the shafts to reach the mineral.

• Ore is broken, hauled to the shaft and lifted to the surface.

• What it needs: lifts, drills, haulage vehicles (to move ore) and ventilation systems that pump fresh air in and push dangerous gases out.

• Risks:
• Poisonous gases (such as methane and carbon monoxide).
• Fires and explosions.
• Floods, when water bursts in.

• Caving in of the roof (roof collapse).

• Indian disasters:

• Jharia coalfield fires (Dhanbad, Jharkhand). Coal seams have been burning underground for decades, and the land above sinks (subsidence).
  • The Jharia Master Plan (JMP) for fire, subsidence and rehabilitation was approved on 12 August 2009. It cost ₹7,112.11 crore and was to run for 10 years, after a 2-year preparation period [6].
  • BCCL (Bharat Coking Coal Ltd) ran 27 fire projects. Methods included surface sealing, digging out burning coal, trenching, pumping in inert gas (a gas that does not burn) and flushing with a sand–bentonite mix [5].
  • Result: surface fire sites fell from 77 to 27, and the fire area fell from 17.32 sq km to 1.80 sq km (2023) [5].
  • The Union Cabinet (CCEA) approved a Revised Jharia Master Plan with ₹5,940.47 crore (2025). It covers resettlement, a ₹1 lakh livelihood grant, and credit support of up to ₹3 lakh for both legal-title and non-legal-title families [6].
• Chasnala disaster (1975): at the Chasnala colliery near Dhanbad (Jharkhand), water flooded the mine and drowned the miners working underground. It is one of India's worst mining disasters.

Feature	Open-cast	Underground (shaft)
Depth of mineral	Near the surface	Deep
Cost	Low	High
Output	Large, fast	Smaller, slower
Safety risk	Low	High (gas, fire, flood, roof collapse)
Main harm	Land scarring, people displaced	Accidents, subsidence, underground fires
India's coal share (2023-24)	~96.6% [7]	3.44% [7]

Other methods

• Placer mining: a placer is a deposit of heavy minerals (gold, tin, diamonds) that rivers have washed down and dropped in sand and gravel. Miners wash the sand, and the heavy minerals settle out.
• Dredging: a dredge (a floating machine) scoops minerals out of river beds or shallow sea floors.
• Offshore drilling: wells are drilled into the sea floor from oil rigs to get petroleum and natural gas. NCERT Fig. 4.18 shows a rig in the Gulf of Mexico.
• Solution mining of lithium brines: a brine is very salty underground water. Lithium is taken from it without digging any rock.
• At Salar de Atacama (a salt flat in northern Chile, in the dry Atacama Desert), lithium-rich brine is pumped up from as deep as 30 m below the salt crust [9].
• Canals carry the brine to evaporation ponds. The dry, windy weather makes the water evaporate quickly [9].
• What remains includes potassium chloride, potassium sulphate, boric acid, magnesium chloride and lithium chloride. Lithium chloride is treated with sodium carbonate to make lithium carbonate, the main raw material of lithium-ion batteries [9].
• Salar de Atacama has the highest lithium concentration in the world. It holds about 6.3 million tonnes of lithium, the largest deposit on Earth that can be mined at a profit [9].
• Argentina's Andean salt flats, Salar del Hombre Muerto and Salar de Olaroz, also produce lithium from brine [10].

The shift in where mining happens

• Developed countries are moving out of mining, processing and refining. The main reason is high labour costs.
• Developing countries with plenty of workers are becoming more important in world mining.
• Mineral-dependent economies are countries that earn over 50% of their income from minerals alone. Several countries in Africa, and a few in South America and Asia, are like this.
• Why this is risky:
• Price volatility: world mineral prices rise and fall sharply, so national income swings with them.
• Resource curse: a country rich in minerals may still grow slowly. Other sectors are neglected, and the mineral money can feed corruption or conflict.

Katanga–Zambia copper belt: minerals attract people

• NCERT (The World Population, Class 12) gives this belt as an example of minerals attracting population (an economic factor of population distribution).
• Location: a copper and cobalt belt on the border of the Democratic Republic of the Congo (DRC) and Zambia, in south-central Africa.
• DRC (Katanga region): Lubumbashi, Kolwezi.

• Zambia (Copperbelt Province): Ndola, Kitwe.

• Transport links (see world-transport-communication):

• Benguela Railway: runs west from the belt to the port of Lobito, Angola, on the Atlantic Ocean.

• TAZARA (Tanzania–Zambia Railway): runs from Kapiri Mposhi (Zambia) east to Dar es Salaam, Tanzania, on the Indian Ocean.

• Cobalt: the DRC mined about 76% of the world's cobalt in 2024, its highest share yet [2] (NCERT-era figure: about 70%). It also holds about 55% of world cobalt reserves (2024) [3].

• The USGS keeps a database of artisanal, small-scale and large-scale mines in the DRC–Zambia Copperbelt [4]. Artisanal mining means mining by hand with simple tools, often unsafe and unregulated. It raises serious child-labour and safety concerns.
• Cobalt is a key battery metal, so the world's electric-vehicle supply chain depends on this one belt.

Prelims Hooks

• Open-cast mining = removal of overburden. It is cheapest, gives quick, large output and has low safety costs. Shaft mining = vertical shafts plus radiating galleries, and it is the riskier method.
• Physical factors of mining: size, grade, mode of occurrence. Demand, technology, capital, labour and transport are economic factors, a common "which of the following" trap.
• India's underground share of coal output: 3.44% (2023-24), falling every year since 2019-20 (5.54%) [7].
• Jharia (Dhanbad, Jharkhand): coal fires. Surface fire area fell from 17.32 to 1.80 sq km; Revised Jharia Master Plan outlay ₹5,940.47 crore [5][6].
• Chasnala disaster, 1975: mine flooding near Dhanbad.
• Katanga–Zambia belt towns: Lubumbashi, Kolwezi (DRC) and Ndola, Kitwe (Zambia). Minerals: copper and cobalt.
• Benguela Railway → Lobito (Angola, Atlantic); TAZARA → Dar es Salaam (Tanzania, Indian Ocean).
• DRC share of world cobalt mine output: ~76% (2024) [2].
• Salar de Atacama (Chile): brine plus evaporation ponds → lithium carbonate. It has the world's highest lithium concentration [9].
• NCERT Fig. 4.18 shows an offshore oil rig in the Gulf of Mexico.

Mains Points

• Changing geography of mining (GS-I): high labour costs and strict environmental rules push developed countries out of mining and refining. Mining moves to labour-rich developing countries in Africa, Latin America and Asia. Many of these become mineral-dependent economies (>50% of income from minerals) and face price swings and the resource curse.
• Open-cast vs underground trade-off (GS-III): India mines ~97% of its coal by open-cast because it is cheap and fast [7]. The cost is scarred land, displaced tribal communities and forest loss. The policy response is mine closure plans, reclamation and afforestation [8]. Underground mining is being promoted again because it disturbs less land.
• Mine disasters and rehabilitation (GS-III, disaster management): Jharia shows how underground fires cause subsidence and air pollution and endanger towns. Scientific fire control (inert gas, sand–bentonite flushing) and the Jharia Master Plan's rehabilitation package with livelihood support form a model response [5][6].
• Critical minerals and supply risk (GS-III): cobalt is concentrated in the DRC (~76% in 2024) and lithium in Andean brines [2][9]. This creates supply-chain risk for EV and energy-storage goals, together with ethical problems of artisanal and child labour. Countries respond by diversifying supply and securing overseas mineral assets.