[very_short_answer] Red soils appear red in colour but turn yellow when found in hydrated form. Name the mineral responsible for this colour difference and identify the type of rock on which red soils typically develop.
Generated by claude-sonnet-4-6 · 2026-06-26 13:29 · grounding rag
Model Answer
The mineral responsible for the colour of red soil is iron. The diffusion of iron in the parent rock gives red soil its characteristic reddish colour. When this iron occurs in a hydrated form, the soil appears yellow.
Red soils typically develop on crystalline igneous rocks (and metamorphic rocks) in areas of low rainfall.
Source: Contemporary India – II, Chapter 1 – Red and Yellow Soils
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Explanation
- The question has two parts: (1) name the mineral, explain colour change; (2) identify the rock type. Both must be answered for full 2 marks.
- The key term is iron (not "iron oxide" specifically, though that is accurate — the textbook just says "iron").
- The rock type must be crystalline igneous rocks (metamorphic is also acceptable as the textbook mentions both, but igneous is primary).
- Avoid writing long paragraphs — two crisp points are enough for 2 marks.