Q1. [3] medium exam-ready
Explain the two main ways in which minerals are formed in sedimentary rocks. Give one example of a mineral formed by each process.
Generated by claude-sonnet-4-6 · 2026-06-26 13:33 · grounding rag
Model Answer
In sedimentary rocks, minerals are formed in two main ways:
- Deposition and concentration in horizontal strata: Minerals accumulate in beds or layers under great heat and pressure over long periods. Example: Coal (and some forms of iron ore).
- Evaporation: In arid regions, water evaporates and leaves behind mineral deposits. Example: Gypsum (also potash salt and sodium salt).
Source: Chapter 5, Mode of Occurrence of Minerals
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Explanation
- The question specifically asks about sedimentary rocks only — do not write about igneous/metamorphic rocks.
- Two distinct processes must be named clearly: (i) deposition/accumulation under heat and pressure and (ii) evaporation in arid regions — each earns 1 mark.
- One correct example per process earns the remaining marks. Coal + Gypsum is the safest pair directly from the textbook.
- Keep examples from the passage; don't guess minerals not mentioned there.