Pumice and obsidian have small crystals so they are?

Pumice and obsidian are classified as volcanic rocks, specifically igneous rocks, and are characterized by their small or lack of crystals due to rapid cooling of lava. Pumice forms when volcanic gas escapes during the cooling process, creating a lightweight, porous texture. In contrast, obsidian forms from the rapid solidification of lava without crystallization, resulting in a glassy appearance. Both rocks are examples of extrusive igneous rocks, formed from lava that cools quickly upon reaching the Earth's surface.