Question

The texture of igneous rocks depends mainly on

• A. Colour of minerals
• B. Rate of cooling of magma
• C. Pressure conditions
• D. Depth of formation

Hint:

Cooling rate determines crystal size: \[ \boxed{ \begin{aligned} \text{Slow cooling} &\rightarrow \text{Large crystals} \text{Fast cooling} &\rightarrow \text{Small crystals} \end{aligned} } \]

Answer 1

The Correct Option is B

Step 1: Recall what determines the texture of igneous rocks. The texture of an igneous rock is mainly determined by the size of its mineral crystals.

Step 2: Relate crystal size to cooling rate. - Slow cooling allows crystals to grow larger, producing a coarse-grained texture. - Rapid cooling forms very small crystals, producing a fine-grained texture. Hence, the texture mainly depends on the \[ \boxed{\text{Rate of cooling of magma}.} \] Therefore, \[ \boxed{(B)} \] is the correct answer.