Rock & Mineral Encyclopedia

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

Banded Iron Formation

Ancient chemically deposited rock of alternating iron-oxide and silica bands recording Earth's early oxygenation and a major iron ore source.

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

Natural volcanic glass speckled with embedded mineral crystals (phenocrysts) such as feldspar or cristobalite that grew before the lava chilled.

A transparent to milky opal that displays a soft bluish-white internal glow or sheen that seems to follow the light source.

The colorless to milky-white variety of beryl, known mineralogically as goshenite and once used to imitate diamond and other gems.

A rare emerald showing a six-spoked star pattern of dark inclusions, named after the spokes of a sugar-mill wheel.