Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Pitchstone

A dull, resinous volcanic glass similar to obsidian but with higher water content and a waxy pitch-like luster.

A rare translucent yellow-green volcanic glass from the Macusani region of Peru, valued by faceters and sometimes confused with tektites.

An opaque, iron-rich basaltic volcanic glass formed by the rapid chilling of basalt lava, darker and denser than rhyolitic obsidian.

A rare breccia formed by meteorite impact, containing shocked rock fragments and glassy melt blobs welded together.