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Difficulty: MediumRocks, Minerals, and Soil

When struck with a rock hammer, a sample of mica easily splits into smooth, paper-thin sheets, while a sample of quartz fractures into irregular, curved shards. Which factor is directly responsible for this difference in how minerals break?

  1. The internal arrangement and relative strength of chemical bonds in the crystal latticeAnswer
  2. B
    The rate at which the molten material cooled during initial crystallization
  3. C
    The degree of surface exposure to physical and chemical weathering agents
  4. D
    The total mass and overall density of the individual mineral specimen

Answer

The internal arrangement and relative strength of chemical bonds in the crystal lattice
Cleavage occurs when a mineral breaks along distinct planar surfaces where the atomic bonds in the crystal lattice are weakest. Mica has a sheet silicate structure with strong bonds within each sheet but very weak bonds between sheets, allowing it to peel into thin layers. Quartz forms a continuous three-dimensional framework of equally strong silicon-oxygen bonds with no preferred planes of weakness, causing it to fracture irregularly.

Step-by-Step Solution

1
Identify the distinct breakage properties described in the question.
Mica exhibits cleavage (splitting along flat, parallel planes), whereas quartz exhibits fracture (irregular or curved breakage).
Classifying the observed behaviors into geological terms is necessary to identify their physical origin.
2
Connect mineral breakage patterns to internal atomic structure.
Cleavage follows planes of weak atomic bonds within the crystal lattice, whereas quartz has uniform bond strength in all directions.
Mineral breakage always follows paths of least structural resistance dictated by atomic bonding.

Key Concept

Mineral Cleavage and Crystal Lattice Structure
Estimated Time:1m 0s
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Topics

Rocks, Minerals, and Soil

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