gemstone

Tumbled agate or chalcedony

Microcrystalline quartz (SiO₂), likely agate/chalcedony with green inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; white to cream, translucent, with green and orange-brown inclusions; vitreous to waxy luster and no visible cleavage. The rounded shape indicates human tumbling and polishing.

Identified August 23, 2026More gemstone →

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Physical properties

Hardness 6.5–7 Mohs; white to cream, translucent, with green and orange-brown inclusions; vitreous to waxy luster and no visible cleavage. The rounded shape indicates human tumbling and polishing.

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing layers of chalcedony and quartz over time; inclusions may be chlorite, celadonite, or iron oxides. Most specimens formed in Cenozoic or older volcanic environments.

Uses & applications

Used for inexpensive jewelry, cabochons, ornaments, and collector specimens; value is mainly decorative.

Geological facts

Agate is a banded variety of chalcedony, while more uniformly colored chalcedony may lack obvious banding. Green coloration is commonly caused by iron- or clay-rich mineral inclusions.

Field identification & locations

Identify by its waxy-to-glassy luster, translucency, very high hardness, and inability to scratch with a steel knife; it should scratch glass. Common sources include Brazil, Uruguay, India, Madagascar, and the western United States.