what type of rock is obsidian

Obsidian is an igneous rock—specifically, a natural volcanic glass formed when lava cools very quickly at the Earth’s surface.

Quick Scoop: What Type of Rock Is Obsidian?

• Obsidian is a volcanic glass, not a crystalline mineral.

• It belongs to the igneous rock family (the same main group as basalt and granite).

• It forms from high-silica, felsic lava that cools so fast crystals don’t have time to grow.

How Geologists Classify It

• Main rock class: igneous (extrusive/volcanic rock).

• Texture: glassy, amorphous (no crystal structure).

• Composition: rich in silica, chemically similar to rhyolite.

In everyday terms, you can think of obsidian as “volcanic glass”: it’s a rock made of frozen lava that turned into glass instead of forming visible crystals.

Fun Extra: Why It Looks So Sharp and Shiny

• Because it’s glassy and brittle, it breaks with very sharp, curved (conchoidal) edges.

• That sharpness made it useful for ancient tools and even experimental surgical blades.

TL;DR: Obsidian is a volcanic glass and counts as an extrusive igneous rock. It forms when high-silica lava cools so fast it becomes glass instead of a crystal-rich stone.

Information gathered from public forums or data available on the internet and portrayed here.