Rock & Mineral Encyclopedia

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

Pineapple Opal

A rare opal pseudomorph from White Cliffs, Australia, formed as opal replaced clustered crystals into a pineapple-like shape.

A shiny, foliated schist studded with red garnet crystals that grew during medium-grade regional metamorphism.

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

A pale chalcedony agate with cloudy, frost-like white patterning suggesting frost on a window or icy crystalline textures.