Rock & Mineral Encyclopedia

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

Peanut Obsidian

Black volcanic glass studded with oval, peanut-shaped grey-white spherulites of radiating crystals frozen in the glass.

A distinctive tourmaline-rich granite from Cornwall, prized as an ornamental stone for its pink feldspar set with radiating black tourmaline.

A striking rock of green zoisite studded with red-pink ruby crystals and black hornblende, also called anyolite.

Tourmaline crystals displaying two or more distinct colors at once, including the famous pink-and-green watermelon variety.

A group of coarse, water-rich plutonic rocks dominated by large hornblende crystals set in feldspar, intermediate between lamprophyre and diorite.

Obsidian that has partly crystallized over time, growing pale spherulite clusters within the black glass, as in snowflake obsidian.