Minerals and Rocks

Why this chapter matters for UPSC: "Minerals and Rocks" was Chapter 5 of Fundamentals of Physical Geography in the pre-2022 NCERT. It was dropped in the rationalisation (Rationalised Edition, December 2022; the current Reprint 2026-27 goes straight from "4. Distribution of Oceans and Continents" to "5. Geomorphic Processes"). The UPSC syllabus still covers it: Mains GS1 2022 asked candidates to "Describe the characteristics and types of primary rocks", which is this chapter's term for igneous rocks. This page follows the old NCERT text and marks clearly what comes from other sources.

Contemporary hook: The Union Cabinet approved the National Critical Mineral Mission on 29 January 2025, with an expenditure of ₹16,300 crore and expected PSU investment of ₹18,000 crore over seven years, covering exploration, mining, beneficiation, processing and recovery from end-of-life products (PIB, 29 January 2025). The minerals it targets occur in the rock types described here.

🧠 First Principles — Read This First

A mineral is a natural substance with an orderly arrangement of atoms and a definite chemical composition, which gives it fixed physical properties such as hardness and colour. Quartz, feldspar and mica are minerals. A rock is an aggregate of one or more minerals. Granite, for example, is mostly feldspar and quartz bound together. A rock has no fixed composition; a mineral does. A brick wall is a fair comparison: the bricks are the minerals and the wall is the rock.

Rocks are grouped into three families by how they form, not by how they look. Igneous rocks form when molten rock (magma below the surface, lava above it) cools and solidifies. NCERT calls them primary rocks because the other two families are derived from them. Sedimentary rocks form when fragments of older rock, or remains of plants and animals, or chemical precipitates settle in layers and are compacted into rock. Metamorphic rocks form when existing rocks are changed by heat and pressure without melting.

These families are linked by the rock cycle. An igneous rock can be broken down into sediment, turned into sedimentary rock, changed by heat and pressure into metamorphic rock, and eventually carried down and melted back into magma. No rock type is permanent.

UPSC cares because rock type controls landforms and soils, and because the minerals in rocks are the country's ore and fuel resources. The old NCERT chapter is also the source of several standard Prelims facts: the eight main elements of the crust, the Mohs hardness scale and the classification of rocks.

PART 1 — Quick Reference

Table 1: The major elements of the Earth's crust (old NCERT Table 5.1)

These eight elements make up about 98 per cent of the crust; the rest includes titanium, hydrogen, phosphorus, manganese, sulphur, carbon and nickel. Source: NCERT FoPG, pre-2022 edition, Chapter 5, p. 40.

Table 2: Physical characteristics of minerals (old NCERT)

Table 3: Mohs hardness scale (old NCERT list)

For comparison NCERT gives a fingernail as 2.5 and glass or a knife blade as 5.5.

Table 4: Major rock-forming minerals (old NCERT)

NCERT adds that chlorite, calcite, magnetite, haematite, bauxite and barite also occur in rocks in some quantities. All six minerals in the table are silicates. Beyond NCERT: silicate minerals make up more than 90 per cent of the Earth's crust (NASA JPL, 2024), and USGS estimates feldspars alone at about 60 per cent of the crust, higher than NCERT's "half".

Table 5: Metallic and non-metallic minerals (old NCERT)

Table 6: The three rock families (old NCERT)

Source: NCERT FoPG, pre-2022 edition, Chapter 5, pp. 42–43. Limestone appears in all three sedimentary groups in NCERT's list because limestone can form in all three ways.

PART 2 — Concepts & Narrative

Elements and minerals

The crust is made of a small number of elements, combined in many ways. Oxygen and silicon alone account for nearly three-quarters of its weight (Table 1). Elements rarely occur alone; they combine into minerals. NCERT defines a mineral as "a naturally occurring organic and inorganic substance, having an orderly atomic structure and a definite chemical composition and physical properties". Most minerals contain two or more elements, but some are single elements: sulphur, copper, silver, gold and graphite.

NCERT's definition includes organic substances, and it describes coal, petroleum and natural gas as organic minerals. Many geology texts use a narrower definition that requires a mineral to be inorganic and crystalline, under which coal is a rock and petroleum is not a mineral at all. For an NCERT-based Prelims question, follow NCERT; in a descriptive answer, note the difference.

NCERT says that "at least 2,000 minerals" had been named and identified, but almost all common ones belong to six major rock-forming groups (Table 4). That count is old. The International Mineralogical Association's commission approved 112 new mineral species in 2023, 103 in 2024 and 86 in 2025 (American Mineralogist, 2026), so the recognised total is now several times NCERT's figure.

NCERT states that the basic source of all minerals is hot magma. As magma cools, mineral crystals appear in a systematic sequence and solidify into rock.

Petrology and why geographers study rocks

Petrology is the science of rocks. A petrologist studies their mineral composition, texture, structure, origin, occurrence, alteration and relationship with other rocks. NCERT's reason for including rocks in a geography book is direct: rocks are closely linked to landforms and to soils. Rocks can be hard or soft (granite is hard, soapstone soft) and of many colours (gabbro is black, quartzite can be milky white). Feldspar and quartz are the most common minerals in rocks.

Igneous rocks

Igneous rocks (Latin ignis, fire) form when magma cools and solidifies. NCERT calls them primary rocks because they form directly from magma and lava from the Earth's interior, and the other families derive from them.

They are classified by texture, which depends on the size and arrangement of grains. Slow cooling at great depth allows large mineral grains to grow. Sudden cooling at the surface produces small, smooth grains. Intermediate conditions produce intermediate grain sizes.

Beyond NCERT, the two textures correspond to two settings (USGS, "What are igneous rocks?"). Intrusive (plutonic) rocks crystallise from magma trapped deep underground, cooling over thousands to millions of years into coarse-grained rocks such as granite, diorite, gabbro and peridotite. Extrusive (volcanic) rocks form when lava cools at or near the surface almost instantly, giving fine-grained or glassy textures, often with gas bubbles trapped as vesicles.

India's best-known extrusive igneous rock is the basalt of the Deccan Traps, a flood-basalt province erupted in pulses around the end of the Cretaceous, about 66 million years ago (Schoene et al., Science, 2019; NCERT's Chapter 4 rounds this to about 60 million years).

Sedimentary rocks

The word comes from the Latin sedimentum, settling. Rocks of every family exposed at the surface are broken into fragments by denudational agents; exogenous agencies transport and deposit these fragments, and compaction turns the deposits into rock. This is lithification. In many sedimentary rocks the original layers remain visible, which is why sandstone and shale show beds of varying thickness.

NCERT classifies them by mode of formation (Table 6): mechanically formed, organically formed and chemically formed. USGS uses the term clastic for rocks made of fragments of pre-existing rock and names them by grain size: shale (clay), siltstone (silt), sandstone (sand) and conglomerate (pebbles larger than 2 mm) (USGS, "What are sedimentary rocks?").

Sedimentary rocks are the main hosts of fossils and of fossil fuels. Fossils occur almost entirely in sedimentary rocks, because organisms are buried in accumulating sediment; heat and pressure usually destroy them in metamorphic rocks, and they cannot survive in melt. India's coal lies mainly in Gondwana sediments of the eastern and central Peninsula, with Gondwana coal also in Assam and Sikkim and younger Tertiary coal in Assam, Arunachal Pradesh, Nagaland and Meghalaya (Indian Bureau of Mines, Indian Minerals Yearbook 2021, Coal and Lignite).

Metamorphic rocks

"Metamorphic" means change of form. These rocks form under changes of pressure, volume and temperature (PVT). NCERT gives three settings: rocks forced down to lower levels by tectonic processes; molten magma rising through the crust and coming into contact with crustal rocks; and underlying rocks put under great pressure by overlying rocks. Metamorphism is the recrystallisation and reorganisation of material within an already consolidated rock.

NCERT's types:

• Dynamic metamorphism: mechanical disruption and reorganisation of minerals by breaking and crushing, without appreciable chemical change.
• Thermal metamorphism: chemical alteration and recrystallisation. It has two forms. In contact metamorphism, rocks touching hot intruding magma or lava recrystallise under high temperature, and new material from the magma is often added. In regional metamorphism, rocks recrystallise because of deformation from tectonic shearing combined with high temperature, pressure or both.

During metamorphism grains or minerals may line up in layers or lines; this is foliation or lineation. When minerals of different groups form alternating light and dark layers, the structure is banding, and such rocks are banded rocks. Metamorphic rocks are grouped as foliated and non-foliated.

Common parent–product pairs, from USGS: shale becomes slate and schist, limestone becomes marble, and sandstone becomes quartzite ("Geology of the New York Region"); granite becomes granite gneiss, a strongly banded rock ("What are metamorphic rocks?"). Limestone has grains that are not flat, so its product, marble, is non-foliated; slate, schist and gneiss are foliated.

The rock cycle

NCERT describes the rock cycle as a continuous process by which old rocks are transformed into new ones. Its sequence:

1. Igneous rocks are primary; sedimentary and metamorphic rocks form from them.
2. Igneous rocks can be changed into metamorphic rocks.
3. Fragments of igneous and metamorphic rocks form sedimentary rocks.
4. Sedimentary rocks can themselves break into fragments that form new sedimentary rocks.
5. Crustal rocks of all three types can be carried down into the mantle by subduction, where plates go down under other plates at convergent boundaries. There they melt into magma, the source of igneous rocks.

NCERT's link to subduction connects this chapter to plate tectonics (Chapter 4). The cycle has no fixed order: any rock can be weathered, metamorphosed or melted, depending on where tectonic processes take it.

Minerals and the economy

Minerals become resources when they can be extracted at a profit. In NCERT's grouping, metallic minerals split into precious, ferrous and non-ferrous metals, and non-metallic minerals include sulphur, phosphates and nitrates (Table 5). Weathering can concentrate valuable ores of iron, manganese, aluminium and copper by leaching away other material; NCERT calls this enrichment (current Chapter 5, "Geomorphic Processes").

Mineral policy is a GS3 topic. The National Critical Mineral Mission (approved 29 January 2025) covers exploration in India and offshore, a fast-track approval process for critical-mineral mining, recovery from overburden and tailings, acquisition of mineral assets abroad, a national stockpile, mineral processing parks and recycling (PIB, 29 January 2025). The same release notes that the Mines and Minerals (Development and Regulation) Act, 1957 was amended in 2023 to increase exploration and mining of critical minerals.

PART 3 — UPSC Integration

PYQ pattern

No direct Prelims question on this chapter is in the bank. Closest adjacent Mains question: gs1-pyq-2017-06 ("In spite of adverse environmental impact, coal mining is still inevitable for development". Discuss.), which concerns coal as a resource rather than rock formation.

Mains frameworks

1. Origin-based classification. For any rock question, organise by origin (igneous, sedimentary, metamorphic), then sub-type, texture or structure, and NCERT's examples.
2. Rock cycle with plate tectonics. Show how the three families convert into each other, ending with NCERT's subduction step that returns crustal rock to magma.
3. Rocks to resources. Link rock family to resource: coal and petroleum in sedimentary basins; ores concentrated by igneous and metamorphic processes and by weathering (enrichment); critical minerals as a current policy theme.

Exam Strategy

Prelims fact-traps:

• Oxygen (46.60%), not silicon, is the most abundant element in the crust by weight; aluminium (8.13%) is the most abundant metal, ahead of iron (5.00%).
• On the Mohs scale topaz is 8 and corundum 9; feldspar (6) is softer than quartz (7).
• Mica is not a single-element mineral; gold, silver, copper, sulphur and graphite are (NCERT exercise).
• Marble is metamorphic, not sedimentary. NCERT's exercise asks which of tillite, borax, breccia and marble is not sedimentary: the answer is marble.
• The two main constituents of granite in NCERT's exercise are silica and aluminium.
• Igneous rocks are "primary rocks" in NCERT.
• NCERT's definition of a mineral includes organic substances; coal, petroleum and natural gas are its examples.
• Diamond is not metamorphosed coal; diamonds form in the mantle and reach the surface in kimberlite.
• Feldspar is about half of the crust (NCERT); pyroxene 10%, amphibole 7%, mica 4%.

Mains question patterns:

• "Characteristics and types" questions want definition, origin, texture or structure, sub-types and examples, in that order.
• Rock-cycle questions want each transformation with its process (cooling, lithification, metamorphism, melting) and the subduction link.

Practice Questions

1. Mains GS1 2022 (10 marks), bank ID gs1-pyq-2022-07: "Describe the characteristics and types of primary rocks."
2. Practice (UPSC-pattern, not a past paper): Arrange the following elements in decreasing order of their share by weight in the Earth's crust: 1. Aluminium 2. Iron 3. Silicon 4. Calcium. (Answer: 3, 1, 2, 4.)
3. Practice (UPSC-pattern, not a past paper): Consider the following pairs of minerals and their positions on the Mohs scale: 1. Calcite — 3; 2. Apatite — 5; 3. Topaz — 9. How many pairs are correctly matched? (Answer: only two; topaz is 8.)
4. Practice (UPSC-pattern, not a past paper): With reference to metamorphic rocks, consider the following statements: 1. Contact metamorphism occurs when rocks recrystallise next to hot intruding magma or lava. 2. Dynamic metamorphism involves appreciable chemical change. 3. Marble is a non-foliated metamorphic rock. Which of the statements are correct? (Answer: 1 and 3 only.)
5. Practice (UPSC-pattern, not a past paper, 150 words): Explain the rock cycle and show how plate tectonics completes it.

📦 Revision Capsule

Sources

Sources

• NCERT, Fundamentals of Physical Geography, Class XI, Chapter 5 "Minerals and Rocks", pre-rationalisation edition, archived copy of http://ncert.nic.in/ncerts/l/kegy205.pdf captured 23 December 2018: https://web.archive.org/web/20181223003132/http://ncert.nic.in/ncerts/l/kegy205.pdf
• NCERT, Fundamentals of Physical Geography, rationalised edition, Reprint 2026-27, contents and Chapter 5 "Geomorphic Processes": https://ncert.nic.in/textbook/pdf/kegy2ps.pdf ; https://ncert.nic.in/textbook/pdf/kegy205.pdf
• Emproto, C. and Olds, T.A. (2026), "New Mineral Names", American Mineralogist 111: 1192–1197: https://msaweb.org/MSA/AmMin/TOC/2026/Abstracts/AM111P1192.pdf
• NASA JPL, "Modeling Silicates and the Chemistry of Earth's Crust" (lesson plan, 11 October 2024): https://www.jpl.nasa.gov/edu/resources/lesson-plan/modeling-silicates-and-the-chemistry-of-earths-crust/
• USGS, "Mineral resource of the month: feldspar" (2004): https://www.usgs.gov/publications/mineral-resource-month-feldspar
• USGS FAQs, "What are igneous rocks?", "What are sedimentary rocks?", "What are metamorphic rocks?": https://www.usgs.gov/faqs/what-are-igneous-rocks ; https://www.usgs.gov/faqs/what-are-sedimentary-rocks ; https://www.usgs.gov/faqs/what-are-metamorphic-rocks
• USGS, "Geology of the New York Region": https://www.usgs.gov/geology-and-ecology-of-national-parks/geology-new-york-region
• Smit, K.V. and Shirey, S.B. (2019), "Kimberlites: Earth's Diamond Delivery System", Gems & Gemology 55(2), GIA: https://www.gia.edu/gems-gemology/summer-2019-kimberlites-earths-diamond-delivery-system
• Schoene, B. et al. (2019), "U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction", Science 363(6429): 862–866: https://oar.princeton.edu/bitstream/88435/pr1ms3k163/1/U-Pb_constraints_pulsed_eruption_Deccan_Traps_end-Cretaceous_mass_extinction.pdf
• Indian Bureau of Mines, Indian Minerals Yearbook 2021, Part III, "Coal & Lignite" (advance release): https://ibm.gov.in/writereaddata/files/16821574626443af961de58Coal_Lignite_2021.pdf
• PIB, "Cabinet Approves 'National Critical Mineral Mission'…", 29 January 2025, Release ID 2097308: https://www.pib.gov.in/PressReleasePage.aspx?PRID=2097308