Final answer:
Coarse-grained rocks have larger crystals compared to fine-grained rocks.
Step-by-step explanation:
Coarse grains form when magma cools slowly underground, while fine grains form when lava cools rapidly on the surface.
The size of the crystals indicates how long the rock took to cool, with slower cooling resulting in larger crystals. Coarse-grained textures are associated with intrusive igneous rocks such as granite, where the magma cools slowly underground allowing crystals to grow to a larger size, often visible to the bare eye. Fine-grained textures are typical in extrusive igneous rocks like basalt, formed when lava cools quickly on the Earth's surface, which does not allow much time for crystal growth.
Coarse-grained rocks often have interlocking crystals that are shiny and fit together like jigsaw puzzle pieces, and these rocks are very hard, able to scratch glass. On the contrary, fine-grained rocks, which cool more quickly, typically have smaller crystals that are harder to distinguish without magnification.