An unknown igneous rock has very small crystals. The rock _____.

Question

cooled quickly
cooled slowly
was formed from dissolved minerals
must be granite

Answer 1

The rock cooled quickly.

When igneous rocks have very small crystals, it typically indicates that they cooled rapidly, often from lava that erupted on the Earth's surface. This rapid cooling does not allow large crystals to form, which is characteristic of rocks like basalt or pumice. In contrast, igneous rocks that cool slowly, such as granite, tend to have larger crystals.