mineral

Banded agate (likely carnelian/chalcedony)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent reddish-brown to gray, waxy to glassy luster, cryptocrystalline quartz, and no visible cleavage. The rough, porous outer surface may be weathered host rock or a vuggy rind.

Identified August 13, 2026More mineral →

Explore Banded agate (likely carnelian/chalcedony) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing successive layers of chalcedony; iron oxides create red-orange hues. Individual agate layers can form over thousands to millions of years, commonly in volcanic terrains.

Uses & applications

Used as ornamental stone, cabochons, beads, carvings, and lapidary specimens; high-quality translucent, strongly banded material has greater jewelry value.

Geological facts

Agate is a variety of chalcedony rather than a separate mineral species. Color may intensify from iron oxides, and some commercial pieces are dyed.

Field identification & locations

Look for curved or concentric banding, waxy luster, translucency at thin edges, and quartz-like hardness that can scratch glass. Common in basalt cavities worldwide, including Brazil, Uruguay, Mexico, India, and the western United States.