Rock & Mineral Encyclopedia

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

Phonolite

A silica-poor volcanic rock of alkali feldspar and feldspathoids that rings when struck, hence 'clinkstone.'

A green-and-white banded metamorphic marble whose wavy mica layers resemble the rings of a sliced onion.

A spotted jasper-rhyolite patterned with leopard-like rings and ovals, valued as an earthy ornamental and lapidary stone.

A banded fortification agate from the remote Dryhead area of south-central Montana, prized for warm concentric rings.

Ancient wood whose organic tissue has been replaced by silica, preserving the grain, rings, and structure of the original tree in stone.

A striking color-zoned tourmaline with a pink center and green rind, resembling a slice of watermelon when cut across the crystal.