Rocks & Minerals
Geography · चट्टानें और खनिज
📋Quick Overview
Rocks are naturally occurring solid aggregates of minerals. There are 3 types: Igneous (formed from cooling magma/lava), Sedimentary (formed from deposition and compaction of sediments), and Metamorphic (formed from existing rocks changed by heat and pressure). These three types continuously transform into each other through the Rock Cycle.
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Igneous rocks are called PRIMARY or PARENT rocks because all other rocks are ultimately derived from them.
📖3 Types of Rocks
| Type | Formation | Examples | Key Features |
|---|---|---|---|
| Igneous | Cooling of magma/lava | Granite (intrusive), Basalt (extrusive), Pumice, Obsidian, Gabbro | No fossils, hardest, primary rocks. Intrusive = cools inside Earth (large crystals). Extrusive = cools on surface (small/no crystals). |
| Sedimentary | Deposition & compaction of sediments over millions of years | Sandstone, Limestone, Shale, Conglomerate, Coal | Contains fossils, layered structure, covers 75% of Earth's surface, softest of the three |
| Metamorphic | Existing rocks changed by heat & pressure | Marble (from Limestone), Slate (from Shale), Quartzite (from Sandstone), Diamond (from Carbon), Gneiss (from Granite) | Foliated or non-foliated, harder than parent rock |
📝Metamorphic Rock Conversions
| Original Rock | Metamorphic Rock |
|---|---|
| Limestone | Marble |
| Sandstone | Quartzite |
| Shale/Clay | Slate |
| Granite | Gneiss |
| Coal | Diamond |
| Slate | Phyllite → Schist |
📝Rock Cycle
- •Igneous → (weathering & erosion) → Sedimentary → (heat & pressure) → Metamorphic → (melting) → Magma → (cooling) → Igneous
- •Any rock type can change into any other type — this continuous process is the Rock Cycle
📖Important Minerals in India
| Mineral | Major Locations in India | Key Facts |
|---|---|---|
| Iron Ore | Odisha (#1 producer), Jharkhand, Chhattisgarh, Karnataka, Goa | India has 4th largest reserves. Types: Hematite (best), Magnetite |
| Bauxite (Aluminium ore) | Odisha (#1), Gujarat, Jharkhand, Maharashtra, Chhattisgarh | Used to make Aluminium. India is 5th largest producer |
| Mica | Jharkhand (#1 — Koderma), Andhra Pradesh, Rajasthan | India was once the world's largest producer. Used in electrical insulation |
| Coal | Jharkhand (#1 — Jharia coalfield, oldest & largest), WB (Raniganj), Odisha, Chhattisgarh, MP | India 2nd largest consumer. Types: Anthracite (best), Bituminous, Lignite, Peat (worst) |
| Petroleum/Oil | Mumbai High (largest offshore), Assam (Digboi — oldest), Gujarat (Ankleshwar), Rajasthan (Barmer) | Digboi = first oil well in India (1889). Mumbai High = largest field. |
| Manganese | Odisha (#1), Karnataka, Madhya Pradesh, Maharashtra, Goa | Used in steel making. India is 5th largest producer. |
📝Mineral Belts of India
- •North-Eastern Plateau Belt — Chota Nagpur Plateau (Jharkhand, Odisha, WB, Chhattisgarh). Richest mineral belt. Coal, iron, manganese, bauxite, mica.
- •South-Western Plateau Belt — Karnataka, Goa, Kerala. Iron ore, manganese, bauxite.
- •North-Western Belt — Rajasthan, Gujarat. Copper, zinc, lead, limestone, gypsum, petroleum.