gemstone

Polished agate/chalcedony fragment

Microcrystalline quartz (SiO₂), likely banded chalcedony or agate

AI-generated identification · may be incorrect

Translucent pale gray-white interior with a brown-golden translucent rim and waxy to vitreous luster; the cut face appears polished. Quartz hardness is 7 Mohs, with no obvious cleavage and conchoidal fracture; specific gravity is about 2.60–2.65.

Identified August 9, 2026More gemstone →

Explore Polished agate/chalcedony fragment 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 quartz in layers over time, commonly during the Cenozoic or older volcanic episodes. The piece has been cut and polished by humans.

Uses & applications

Used for cabochons, beads, carvings, tumblestones, and ornamental objects; durable enough for jewelry and small decorative work.

Geological facts

Agate is defined by chalcedony or quartz banding, although this fragment’s limited visible layering makes exact identification uncertain. The brown edge may reflect iron-oxide staining.

Field identification & locations

Look for waxy translucency, curved/conchoidal fracture, hardness sufficient to scratch glass, and natural curved banding; it is commonly found in volcanic regions worldwide, including Brazil, Uruguay, India, Madagascar, and the United States. Avoid confusing it with colored glass or resin.