gemstone

Tumbled agate or chalcedony (probable)

Microcrystalline quartz, SiO₂

AI-generated identification · may be incorrect

Small polished pebble with gray-blue and tan coloration, waxy-to-glassy luster, and likely cryptocrystalline structure; Mohs hardness 6.5–7, no visible cleavage, specific gravity about 2.60–2.65. The image is insufficient to confirm banding or exact variety.

Identified September 6, 2026More gemstone →

Explore Tumbled agate or chalcedony (probable) 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 rock, depositing chalcedony and sometimes quartz in layers; ages range from Paleozoic to modern, depending on locality. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and small display specimens; common tumbled pieces have modest value.

Geological facts

Agate is a variety of chalcedony distinguished by banding, while uniformly colored material may be called chalcedony or jasper depending on opacity and impurities.

Field identification & locations

Identify by its very hard, smooth polish, waxy appearance, and resistance to scratching by steel; glass should not scratch it. Strong banding, translucency, or a drusy quartz surface would support an agate identification.