gemstone

Tumbled agate (likely carnelian or banded chalcedony)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; cream, tan, and orange-brown colors with subtle curved banding; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage. The rounded shape indicates tumbling or natural abrasion.

Identified August 16, 2026More gemstone →

Explore Tumbled agate (likely carnelian or banded chalcedony) in the encyclopedia →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony in layers; iron impurities create the warm colors. Most agates formed during the Cenozoic to Paleozoic eras, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and lapidary collections; durable enough for jewelry and small decorative objects.

Geological facts

Agate banding records successive changes in the chemistry of the cavity-filling fluids. The specimen may also be marketed as carnelian if its orange-red chalcedony is mostly translucent and lacks obvious banding.

Field identification & locations

Check for translucency at the edges, curved or concentric bands, a glass-scratching hardness, and a cool, dense feel; common sources include Brazil, Uruguay, India, Madagascar, and the western United States. Exact identification requires a close view or testing.