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Comprehensive DGMS Geology Notes covering the occurrence, geological setting, and Indian distribution of Chromite and Bauxite deposits. Includes 25 solved MCQs for DGMS and Mining Geology exam aspirants.
  🔹 1. Introduction

Chromite and Bauxite are two of India’s most vital metallic and industrial minerals.

• Chromite (FeO·Cr₂O₃) is the principal ore of chromium, a metal essential in the stainless steel and alloy industry.
  
• Bauxite (Al₂O₃·2H₂O) is the main source of aluminum, widely used in electrical, transport, and packaging sectors.
  

Both minerals have strong economic and strategic importance and form a key part of DGMS mining geology syllabus.

🔹 2. Chromite – Ore, Composition & Properties

Property	Description
Chemical Formula	FeO·Cr₂O₃
Specific Gravity	4.1–4.6
Color	Iron-black to brownish-black
Luster	Metallic to submetallic
Hardness	5.5
Associated Minerals	Magnetite, Olivine, Serpentine, Pyroxene
Mode of Occurrence	Stratiform & Podiform bodies in ultramafic rocks

🔹 3. Geological Setting of Chromite Deposits

Chromite occurs mainly in ultramafic and mafic igneous rocks, especially dunite, peridotite, and serpentinized rocks.
It forms by magmatic segregation and often occurs as pod-like or lenticular bodies.Typical associations:

• Dunite–Peridotite complexes
  
• Ophiolite belts (Sukinda, Nuasahi, etc.)
  
• Layered intrusions of Precambrian age
  

🔹 4. Distribution of Chromite in India

State	Major Deposits	Notes
Odisha	Sukinda Valley (Jajpur), Nuasahi (Keonjhar)	~98% of India’s chromite resources
Karnataka	Chitradurga, Hassan, Shimoga	Podiform type in ultramafics
Maharashtra	Bhandara, Ratnagiri	Small scattered deposits
Jharkhand	Roro–Jojohatu (Singhbhum)	Minor chromite occurrences

🔸 Sukinda Valley (Odisha) – World-famous for high-grade ferrochrome ores and hosts India’s largest chromite reserves.

🔹 5. Bauxite – Composition & Properties

Property	Description
Main Ore Minerals	Gibbsite (Al(OH)₃), Boehmite (AlO(OH)), Diaspore (AlO(OH))
Color	Whitish to reddish-brown
Texture	Earthy, pisolitic
Formation	Residual & lateritic from leaching of alumina-rich rocks
Chemical Formula	Al₂O₃·2H₂O
Economic Use	Source of aluminum metal

🔹 6. Geological Setting of Bauxite Deposits

Bauxite forms due to lateritic weathering of aluminum-rich rocks such as basalts, granites, and khondalites in tropical climates.
It commonly occurs as caps or blankets over plateaus and hilltops.

Types:

1. Lateritic Bauxite – residual accumulation on basalt or granite.
   
2. Sedimentary Bauxite – re-deposited in basins.
   

🔹 7. Distribution of Bauxite in India

State	Major Deposits	Geological Note
Odisha	Panchpatmali Hills, Damanjodi	High-grade, lateritic origin
Jharkhand	Lohardaga, Latehar	Residual type
Chhattisgarh	Mainpat Plateau, Ambikapur	Lateritic over Deccan traps
Madhya Pradesh	Katni, Balaghat	Associated with Vindhyan rocks
Maharashtra	Kolhapur, Ratnagiri	Lateritic caps
Tamil Nadu	Shevroy Hills	Small pockets

🔹 8. Economic ImportanceChromite:

• Used in stainless steel, refractory bricks, and chemicals.
  
• Vital for ferrochrome alloys.
  

Bauxite:

• Primary source of aluminum production.
  
• Used in cement, abrasives, and refractories.
  
• India ranks 6th globally in bauxite reserves.
  

🧠 9. 25 Objective Questions with Answers

1️⃣ The most important ore mineral of copper is —

a) Bornite
b) Chalcopyrite
c) Chalcocite
d) Covellite
e) Malachite
✅ Answer: b) Chalcopyrite

---

2️⃣ Malanjkhand copper deposit is located in —

a) Odisha
b) Madhya Pradesh
c) Jharkhand
d) Rajasthan
e) Maharashtra
✅ Answer: b) Madhya Pradesh

---

3️⃣ Khetri Copper Belt lies in which geological group?

a) Dharwar Supergroup
b) Delhi Supergroup
c) Cuddapah Supergroup
d) Vindhyan Group
e) Aravalli Group
✅ Answer: b) Delhi Supergroup

---

4️⃣ Singhbhum Shear Zone is famous for —

a) Iron
b) Copper
c) Gold
d) Lead
e) Bauxite
✅ Answer: b) Copper

---

5️⃣ The largest lead-zinc mine in India is —

a) Rajpura-Dariba
b) Rampura-Agucha
c) Zawar
d) Agnigundala
e) Sargipalli
✅ Answer: b) Rampura-Agucha

---

6️⃣ Galena is an ore mineral of —

a) Zinc
b) Lead
c) Copper
d) Silver
e) Gold
✅ Answer: b) Lead

---

7️⃣ Sphalerite is also known as —

a) Zinc blende
b) Pyrolusite
c) Chalcopyrite
d) Cassiterite
e) Malachite
✅ Answer: a) Zinc blende

---

8️⃣ The formula of galena is —

a) PbS
b) ZnS
c) CuFeS₂
d) FeS₂
e) PbCO₃
✅ Answer: a) PbS

---

9️⃣ Lead-zinc deposits in Rajasthan occur mainly in —

a) Shale formations
b) Dolomitic limestones and phyllites
c) Sandstones
d) Quartzites
e) Basalts
✅ Answer: b) Dolomitic limestones and phyllites

---

🔟 The main associated mineral with Pb-Zn deposits is —

a) Chalcopyrite
b) Pyrite
c) Barite
d) Both (a) and (b)
e) None of these
✅ Answer: d) Both (a) and (b)

---

11️⃣ The largest copper producer in India is —

a) Rajasthan
b) Jharkhand
c) Madhya Pradesh
d) Odisha
e) Gujarat
✅ Answer: c) Madhya Pradesh

---

12️⃣ Hutti Gold Mines are located in —

a) Tamil Nadu
b) Andhra Pradesh
c) Karnataka
d) Jharkhand
e) Rajasthan
✅ Answer: c) Karnataka

---

13️⃣ The Kolar Gold Field is associated with —

a) Dharwar schists
b) Cuddapah sediments
c) Vindhyan limestones
d) Aravalli phyllites
e) Gondwana sandstones
✅ Answer: a) Dharwar schists

---

14️⃣ The ore mineral of gold is —

a) Auriferous pyrite
b) Electrum
c) Native gold
d) All of these
e) None of these
✅ Answer: d) All of these

---

15️⃣ The Rampura-Agucha deposit is mainly of —

a) Magmatic origin
b) Hydrothermal origin
c) Sedimentary origin
d) Placer origin
e) Metamorphic origin
✅ Answer: b) Hydrothermal origin

---

16️⃣ Zawar mines are located in —

a) Bhilwara district
b) Rajsamand district
c) Udaipur district
d) Jaipur district
e) Chittorgarh district
✅ Answer: c) Udaipur district

---

17️⃣ The chief ore mineral of zinc is —

a) Sphalerite
b) Smithsonite
c) Franklinite
d) Willemite
e) Zincite
✅ Answer: a) Sphalerite

---

18️⃣ Copper deposits in Singhbhum district occur along —

a) Fault zones
b) Shear zones
c) Folds
d) Anticlines
e) Dyke contacts
✅ Answer: b) Shear zones

---

19️⃣ The main ore mineral of lead is —

a) Cerussite
b) Anglesite
c) Galena
d) Pyromorphite
e) Wulfenite
✅ Answer: c) Galena

---

20️⃣ The metal most commonly associated with gold is —

a) Silver
b) Copper
c) Lead
d) Zinc
e) Iron
✅ Answer: a) Silver

---

21️⃣ Khetri copper ores occur in —

a) Quartz veins
b) Dolomite lenses
c) Schistose rocks
d) Gneissic zones
e) Granite intrusions
✅ Answer: c) Schistose rocks

---

22️⃣ Which of the following is a secondary ore of copper?

a) Chalcocite
b) Chalcopyrite
c) Pyrite
d) Galena
e) Hematite
✅ Answer: a) Chalcocite

---

23️⃣ Which gold mine in India is one of the deepest in the world?

a) Hutti
b) Kolar
c) Gadag
d) Ramagiri
e) Anantapur
✅ Answer: b) Kolar

---

24️⃣ Rajpura-Dariba mine produces —

a) Iron and manganese
b) Lead and zinc
c) Gold and silver
d) Copper and bauxite
e) Uranium and thorium
✅ Answer: b) Lead and zinc

---

25️⃣ DGMS classifies Cu, Pb, Zn & Au deposits under —

a) Precious minerals
b) Energy minerals
c) Metallic minerals
d) Non-metallic minerals
e) Industrial minerals
✅ Answer: c) Metallic minerals

🧾 10. Quick Recap

Mineral	Key Ore	Major State	Type	Economic Use
Chromite	FeO·Cr₂O₃	Odisha	Magmatic	Ferroalloy, steel
Bauxite	Al₂O₃·2H₂O	Odisha, Jharkhand	Lateritic	Aluminum metal

                    🔚 11. Conclusion

Chromite and Bauxite together play a crucial role in India’s metallurgical and industrial framework.
While Odisha dominates both, Jharkhand and Chhattisgarh follow in bauxite reserves.
Understanding the geological occurrence, state-wise distribution, and mineral characteristics of these deposits is essential for all DGMS and GATE Geology aspirants, as questions frequently appear in the DGMS MMCC, Overman, and Manager’s exams.

💡 Are you preparing for DGMS Mining Geology exams?
👉 Continue your learning journey with the next article in our DGMS Geology Notes Series — “Copper, Lead, Zinc & Gold Deposits in India – Distribution & Major Mines.”
📘 Access PDF notes, mock tests, and quizzes on OnlineMiningExam.com.
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