Some important MCQs with explanations related to Economic Geology for the Jharkhand Academic Council (JAC) 12th Exam -1

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1. What is economic geology?

a) The study of rocks and minerals
b) The study of economically valuable earth materials
c) The study of fossil fuels
d) The study of Earth's crust

Answer: b) The study of economically valuable earth materials
Explanation:
Economic geology focuses on materials that can be extracted from the Earth for economic gain, such as minerals, ores, coal, and petroleum.
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2. Which mineral is the primary source of aluminum?

a) Hematite
b) Bauxite
c) Galena
d) Magnetite

Answer: b) Bauxite
Explanation:
Bauxite is the primary ore of aluminum, consisting of hydrated aluminum oxides and hydroxides.

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3. What is an ore?

a) A type of sedimentary rock
b) A naturally occurring rock or mineral from which a metal can be profitably extracted
c) A type of igneous intrusion
d) A mineral with no economic value

Answer: b) A naturally occurring rock or mineral from which a metal can be profitably extracted
Explanation:
An ore contains enough valuable minerals to make mining and extraction economically feasible.

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4. Which type of deposit forms from hydrothermal fluids?

a) Placer deposits
b) Sedimentary deposits
c) Magmatic deposits
d) Vein deposits

Answer: d) Vein deposits
Explanation:
Hydrothermal fluids deposit minerals in cracks and fractures, forming vein deposits rich in metals like gold, silver, and copper.

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5. What is the principal ore mineral of lead?

a) Galena
b) Sphalerite
c) Cassiterite
d) Pyrite

Answer: a) Galena
Explanation:
Galena (PbS) is the most important ore mineral for lead, often found in hydrothermal deposits.

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6. Which of the following is a fossil fuel?

a) Limestone
b) Quartz
c) Coal
d) Magnetite

Answer: c) Coal
Explanation:
Coal is a fossil fuel formed from the accumulation and compression of plant material over millions of years.

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7. What type of deposit is associated with alluvial and river environments?

a) Magmatic deposits
b) Placer deposits
c) Hydrothermal deposits
d) Metamorphic deposits

Answer: b) Placer deposits
Explanation:
Placer deposits form when heavy minerals, such as gold and diamonds, are concentrated by water flow in alluvial and river environments.
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8. What is the main mineral used for cement production?

a) Calcite
b) Hematite
c) Magnetite
d) Feldspar

Answer: a) Calcite
Explanation:
Calcite (CaCO₃), commonly found in limestone, is a primary raw material for cement manufacturing.
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9. Which of the following minerals is the primary source of iron?

a) Galena
b) Hematite
c) Bauxite
d) Quartz

Answer: b) Hematite
Explanation:
Hematite (Fe₂O₃) is a major ore of iron, widely used in steel production.
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10. What type of economic deposit is formed by the cooling of magma?

a) Sedimentary deposits
b) Magmatic deposits
c) Placer deposits
d) Hydrothermal deposits

Answer: b) Magmatic deposits
Explanation:
Magmatic deposits form directly from the crystallization of magma and include minerals like chromite and magnetite.
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11. What is the primary ore mineral for zinc?

a) Galena
b) Sphalerite
c) Chalcopyrite
d) Pyrolusite

Answer: b) Sphalerite
Explanation:
Sphalerite (ZnS) is the most important ore mineral for extracting zinc.

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12. Which process concentrates economically valuable minerals by gravity?

a) Hydrothermal activity
b) Magmatic differentiation
c) Placer formation
d) Metamorphism

Answer: c) Placer formation
Explanation:
Placer formation occurs when heavier minerals settle out of moving water due to gravity, concentrating them in specific locations.

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13. Which rock type is commonly associated with petroleum reservoirs?

a) Granite
b) Sandstone
c) Basalt
d) Gneiss

Answer: b) Sandstone
Explanation:
Sandstone is a porous and permeable sedimentary rock, making it an excellent reservoir for oil and gas.

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14. What is the principal ore of copper?

a) Magnetite
b) Chalcopyrite
c) Galena
d) Cassiterite

Answer: b) Chalcopyrite
Explanation:
Chalcopyrite (CuFeS₂) is the most important ore mineral for copper extraction.
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15. What is the primary method for extracting gold from low-grade ores?

a) Magnetic separation
b) Heap leaching
c) Flotation
d) Smelting

Answer: b) Heap leaching
Explanation:
Heap leaching involves using cyanide solutions to extract gold from low-grade ores, a widely used method in modern mining.

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