Rock & Mineral Encyclopedia

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

Petrified Wood

Ancient wood whose organic tissue has been replaced by silica, preserving the grain, rings, and structure of the original tree in stone.

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

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

Fossilized wood in which the original organic structure has been replaced by opal, sometimes showing precious play-of-color.