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🌏 Introduction 

Mineral deposits occur in various geological environments depending on the formation process and rock type.
In India, the occurrence of metallic and non-metallic minerals is governed by tectonic setting, rock association, and geological history.

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🪨 Types of Geological Environments & Associated Minerals 

  1️⃣ Volcano-Sedimentary Sequences (Igneous + Sedimentary Rocks)

• Typical Ores: Cu, Pb, Zn, Fe, Mn, Au, W, U, Mo
• Example: Khetri Copper Belt (Rajasthan), Zawar Pb-Zn (Rajasthan)

2️⃣ Sedimentary Rocks

• Ores: Iron, Manganese, Magnesium, Phosphorite, Base Metals
• Example: Iron ore of Singhbhum (Jharkhand), Manganese of Balaghat (MP)

3️⃣ Ultramafic Rocks (Igneous)

• Ores: Platinum Group Elements (PGE), Chromite, Nickel, Diamond
• Example: Sukinda (Odisha) – Chromite, Panna (MP) – Diamond

4️⃣ Acid to Intermediate Igneous Rocks

• Ores: Copper, Molybdenum, Gold
• Example: Malanjkhand Copper (MP), Kolar Gold Fields (Karnataka)

5️⃣ Igneous & Metamorphic Rocks

• Ores: Tin (Sn), Tungsten (W), Mica
• Example: Hazaribagh Mica Belt (Jharkhand), Tosham Tungsten (Haryana)

6️⃣ Metamorphic Rocks

• Ores: Sillimanite, Kyanite, Gemstones (Sapphire)
• Example: Kharswan (Jharkhand), Koraput (Odisha)

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⚙️ Modes of Occurrence of Ore Deposits

Mode	Description	Example
Bedded / Layered	Minerals form stratified layers	Banded Iron Formation (BIF)
Vein Type	Minerals deposited from hydrothermal fluids	Galena, Chalcopyrite
Pocket Type	Small irregular accumulations	Gold pockets, Pegmatites
Massive Type	Large homogenous ore body	Chromite, Magnetite
Replacement Type	Ore replaces host rock material	Lead-Zinc in limestone

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🧭 DGMS Exam Focus Points

• Host rock–ore association
• Examples of Indian mineral belts
• Modes of occurrence (Bedded, Vein, Massive)
• Deposit identification by rock type
• Common exam question: “Chromite occurs in which rock type?”
• 
  
• 🧠 25 DGMS MCQs with 5 Options and Detailed Solutions

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  Q1. The richest iron ore deposits of India are found in:
  A. Goa
  B. Odisha
  C. Rajasthan
  D. MP
  E. Gujarat
  Answer: B
  Solution: Odisha’s Keonjhar and Sundargarh host high-grade hematite BIF ores.

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  Q2. The main copper belt of India lies in:
  A. Karnataka
  B. Rajasthan
  C. Jharkhand
  D. MP
  E. Odisha
  Answer: B
  Solution: Khetri belt (Rajasthan) has extensive hydrothermal copper veins.

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  Q3. Manganese ore of India is mainly of:
  A. Magmatic origin
  B. Residual origin
  C. Sedimentary–Lateritic origin
  D. Metamorphic origin
  E. Hydrothermal origin
  Answer: C
  Solution: Indian manganese mostly forms as residual laterites and sedimentary layers.

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  Q4. Bauxite deposits in India are formed by:
  A. Hydrothermal replacement
  B. Weathering and residual concentration
  C. Magmatic segregation
  D. Sedimentary layering
  E. Evaporation
  Answer: B
  Solution: Bauxite is residual, from lateritic weathering of aluminous rocks.

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  Q5. Lead-Zinc deposits of Rajasthan are:
  A. Sedimentary
  B. Placer
  C. Hydrothermal replacement type
  D. Magmatic segregated
  E. Evaporitic
  Answer: C
  Solution: Zawar, Rajpura-Dariba deposits are hydrothermal replacement.

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  Q6. The mineral monazite occurs mainly in:
  A. Desert sands
  B. Coastal sands
  C. River gravel
  D. Igneous rocks
  E. Bauxite crusts
  Answer: B
  Solution: Monazite is a placer mineral found in Kerala–TN beach sands.

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  Q7. Iron ore in Bailadila is of:
  A. Sedimentary BIF type
  B. Magmatic segregated type
  C. Residual type
  D. Placer type
  E. Metamorphic type
  Answer: A
  Solution: Bailadila ores occur in Precambrian Banded Iron Formations.

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  Q8. Gold deposits of Kolar are:
  A. Placer
  B. Lode (vein) type
  C. Bedded
  D. Residual
  E. Magmatic
  Answer: B
  Solution: Kolar Gold Fields – hydrothermal lode veins in schists.

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  Q9. Chromite deposits in Sukinda are:
  A. Hydrothermal
  B. Sedimentary
  C. Magmatic segregation
  D. Placer
  E. Metamorphic
  Answer: C
  Solution: Chromite crystallized early during magmatic differentiation.

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  Q10. Petroleum accumulates in:
  A. Igneous traps
  B. Porous sedimentary traps
  C. Magmatic pipes
  D. Alluvial plains
  E. Fault zones
  Answer: B
  Solution: Petroleum found in porous sandstones capped by impermeable strata.

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  Q11. Magnesite occurs mainly in:
  A. Sedimentary rocks
  B. Ultramafic rocks & metamorphic zones
  C. Igneous intrusive bodies
  D. Sand beds
  E. Alluvial layers
  Answer: B
  Solution: Magnesite forms through alteration of serpentinites.

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  Q12. Placer deposits form due to:
  A. Weathering concentration
  B. Sedimentation and current action
  C. Chemical replacement
  D. Hydrothermal alteration
  E. Evaporation
  Answer: B
  Solution: Placer = mechanical concentration by river or wave action.

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  Q13. Major coalfields of India belong to:
  A. Gondwana rocks
  B. Archaean rocks
  C. Cretaceous rocks
  D. Tertiary limestones
  E. Dharwar schists
  Answer: A
  Solution: Gondwana Supergroup (Permian) hosts major coalfields.

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  Q14. Limestone deposits of Chhattisgarh are:
  A. Igneous
  B. Sedimentary
  C. Metamorphic
  D. Magmatic
  E. Placer
  Answer: B
  Solution: Bedded sedimentary limestone, used in cement industry.

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  Q15. Gypsum is found mainly in:
  A. Odisha
  B. Rajasthan
  C. Kerala
  D. Bihar
  E. MP
  Answer: B
  Solution: Gypsum occurs in T
  

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🏁 Conclusion 

Knowledge of mineral distribution helps in targeted exploration and efficient mine planning.
DGMS aspirants must remember rock–ore associations and Indian examples, as they are frequently asked in oral and written exams.

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 Boost Your DGMS Geology Preparation with Practical Notes!
Learn mineral distribution, host rock relations, and occurrence patterns in one place.
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