Rock & Mineral Encyclopedia

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

Red Agate

A red-toned banded chalcedony colored by iron oxides, ranging from natural carnelian-like reds to heat-treated stones.

A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.

A white to grayish banded chalcedony, the natural base color of much agate and the substrate for many dyed stones.