Question

What characterizes a porphyritic texture in igneous rocks?

• A. Layers of alternating light and dark minerals
• B. A texture in which some crystals are distinctly larger than the rest
• C. Crystals that form only from volcanic eruptions
• D. Uniformly sized crystals throughout the rock

Hint:

Porphyritic = "mixed crystals" — big crystals in a finer background due to different cooling rates.

Answer 1

The Correct Option is B

Porphyritic texture in igneous rocks indicates a two-stage cooling process where large crystals (phenocrysts) form slowly below the surface followed by rapid cooling that creates a fine-grained matrix. This results in a mix of crystal sizes.