Rock & Mineral Encyclopedia

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

Turritella Jasper

A fossiliferous jasper packed with spiral snail shells, technically a silicified gastropod limestone from Wyoming.

Fossil material whose original substance has been replaced by opal, preserving ancient shapes in common or play-of-color opal.

Calcium-carbonate sedimentary rock packed with visible fossils, recording ancient marine life within an easily scratched, fizzing matrix.

Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.

A limestone packed with visible shells and shell fragments, recording the accumulation of marine invertebrate remains on ancient sea floors.

A lightweight black organic gemstone formed from fossilized wood under pressure, a type of lignite long used in mourning jewelry.

Fossilized tree resin, warm and lightweight, sometimes preserving ancient insects and plant matter inside.

Ancient wood whose organic tissue has been replaced by silica, preserving the grain, rings, and structure of the original tree in stone.

A quartz crystal containing pink to lilac lithium-bearing mineral inclusions that give a soft cloudy lavender or rose coloration.