Which one of the following is not an igneous rock ?
- A.Gabbro
- B.Granite
- C.Dolomite
- D.Basalt
Correct answer
Explanation
The correct answer is C, Dolomite. Dolomite is a sedimentary rock, not an igneous one; it forms from layers of carbonate deposits laid down in water.
Dolomite is made mostly of the mineral dolomite, a carbonate of calcium and magnesium, CaMg(CO3)2. It usually forms when magnesium-rich water alters limestone. Igneous rocks, by contrast, form when molten magma or lava cools and hardens. They are called primary rocks because all other rocks are ultimately formed from them. Igneous rocks that cool slowly deep inside the earth have large crystals (intrusive), while those that cool fast on the surface have small crystals (extrusive).
A is wrong: gabbro is a coarse-grained intrusive igneous rock, rich in iron and magnesium. B is wrong: granite is a coarse-grained intrusive igneous rock rich in silica, common in the Peninsular plateau. D is wrong: basalt is a fine-grained extrusive igneous rock; the Deccan Traps are made of it.
Exam tip: Granite and gabbro are intrusive, basalt is extrusive; limestone and dolomite are sedimentary.
Practice Questions
View allWhich one among the following is the most populated State in India as per Census 2011?
- A.Goa
- B.Mizoram
- C.Meghalaya
- D.Sikkim
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- A.1 only
- B.2 and 3 only
- C.1 and 2 only
- D.1, 2 and 3
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- A.Subtropical steppe
- B.Humid sub-tropical climate
- C.Cold climate with dry winters
- D.Tundra climate
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- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
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Read the full explanation →ISRO, in its studies, has revealed that there is a 178% increase in the size of the Ghepang Ghat Glacial Lake. In which of the following States/UTs is this lake located ?
- A.Jammu & Kashmir
- B.Ladakh
- C.Himachal Pradesh
- D.Uttarakhand
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