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Difficulty: MediumRock Types, Formation, and Economic Importance

Match each rock specimen in Column A with its corresponding formation process and distinct characteristic or economic utility in Column B.

  • PegmatiteExtremely coarse-grained intrusive igneous rock enriched in rare minerals such as mica, tourmaline, and beryl.
  • TravertineChemically precipitated sedimentary rock formed by rapid calcium carbonate deposition at geothermal springs and limestone caves.
  • HornfelsNon-foliated metamorphic rock formed through high-temperature contact metamorphism adjacent to magmatic intrusions.
  • Bituminous CoalOrganically formed sedimentary rock derived from accumulated plant debris, widely utilized for industrial thermal power generation.

Answer

Pegmatite matches with the extremely coarse-grained intrusive igneous rock enriched in rare minerals; Travertine matches with the chemically precipitated sedimentary rock formed by rapid calcium carbonate deposition; Hornfels matches with the non-foliated metamorphic rock formed through contact metamorphism; Bituminous Coal matches with the organically formed sedimentary rock derived from accumulated plant debris.
Each rock specimen is correctly matched to its distinct genesis: Pegmatite represents intrusive igneous crystallization with oversized crystals, Travertine represents chemical sedimentary carbonate precipitation, Hornfels represents thermal contact metamorphism, and Bituminous Coal represents organic sedimentary compaction of carbon-rich plant material.

Step-by-Step Solution

1
Analyze the formation process of Pegmatite
Pegmatite forms from slow cooling of mineral-rich magmatic fluids, resulting in huge interlocking crystals containing rare elements.
This places Pegmatite squarely under intrusive igneous rock genesis.
2
Analyze the formation process of Travertine
Travertine precipitates directly out of solution where groundwater rich in dissolved bicarbonate emerges at springs or in caves.
This classifies Travertine as a chemical sedimentary rock.
3
Analyze the formation process of Hornfels
Hornfels forms when existing rock is baked by local magmatic heat without intense directional pressure.
This identifies Hornfels as a product of thermal contact metamorphism.
4
Analyze the formation process of Bituminous Coal
Bituminous coal develops from peat deposited in ancient swamp environments subjected to deep burial and compaction over geological time.
This categorizes Bituminous Coal as an organic sedimentary rock.

Key Concept

Rock Types, Genesis, and Economic Characteristics
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Topics

Rock Types, Formation, and Economic Importance

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