Chalcedony is a smooth, waxy-looking type of quartz that comes in many colors and has been prized for thousands of years. Unlike clear crystal quartz, chalcedony has a cloudy or translucent appearance, and it often forms in layers of different colors that create beautiful patterns.

Ancient craftspeople carved chalcedony into seals, jewelry, and decorative objects because it's hard enough to hold fine details but soft enough to work with hand tools. The famous cameos worn by Roman emperors were often carved from banded chalcedony. You might recognize some of chalcedony's colorful varieties by their own names: agate has distinctive stripes, onyx shows bands of black and white, carnelian glows orange-red, and chrysoprase shines apple green.

Geologists find chalcedony in volcanic rocks, where mineral-rich water slowly deposits microscopic quartz crystals in cracks and cavities. The different colors come from trace amounts of other minerals mixed in as the chalcedony forms. Today, people still use chalcedony in jewelry and collections, appreciating the same smooth texture and subtle beauty that attracted ancient craftspeople millennia ago.