Rock & Mineral Encyclopedia

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

Coquina

A soft, porous limestone made of loosely cemented shell and coral fragments, used as a coastal building stone.

A soft, sky-blue strontium sulfate mineral famous for the glittering pale-blue crystal geodes from Madagascar.

A soft pale-blue calcium sulfate, the anhydrous form of gypsum, prized as a gentle, calming tumbled stone.

A pale translucent chalcedony threaded with brown-black manganese and iron dendrites that mimic tiny ferns, mosses or landscapes.

A finely speckled pale jasper trade stone named for its sesame-seed-like flecks, closely related to Kiwi Jasper.

A glassy calcium borosilicate forming wedge-tipped prismatic crystals, usually colorless to pale yellow or pink, sometimes faceted as a gem.

Glacially deposited banded agates found along Lake Michigan beaches, small waterworn pebbles with concentric red and grey banding.

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

A dark jasper trade stone speckled with pale flecks resembling a starry night sky, valued for its cosmic appearance.

A warm-toned jasper named for its autumn-leaf palette of browns, rust, gold, and cream, popular as soothing earth-tone beads.