Question

Difference between obsidian and volcanic rock crystal

Answer 1

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. ... The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth.

Volcanic or extrusive rock. This is rock that is formed on the surface of the earth. In contact with air or seawater, molten rock cools rapidly and either quenches to a glass (like obsidian) or forms small crystals (basalt). Volcanic rocks are usually finely grained or glassy in structure.