sedimentary

Banded Agate

Silicon Dioxide (SiO2) - Chalcedony

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs. Color: Gray, purple, brown, and translucent bands. Luster: Vitreous to waxy. Structure: Cryptocrystalline. Cleavage: None. Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Gray, purple, brown, and translucent bands
Luster: Vitreous to waxy

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs. Color: Gray, purple, brown, and translucent bands. Luster: Vitreous to waxy. Structure: Cryptocrystalline. Cleavage: None. Specific Gravity: 2.58-2.64.

Formation & geological history

Agate forms as a secondary mineral in nodules within volcanic and sedimentary rocks. Silica-rich groundwater fills cavities (gas bubbles in lava), depositing layers of chalcedony over thousands of years. This piece specifically appears to be a tumbled river stone or lapidary-polished pebble.

Uses & applications

Commonly used in jewelry, lapidary arts, metaphysical practices, and industrial mortars/pestles due to its hardness and chemical resistance.

Geological facts

The distinct bands are caused by variations in the composition of the silica-rich fluids during formation. It was one of the earliest stones used for amulets and seals in ancient Mesopotamia and Egypt.

Field identification & locations

Identify by its translucent nature, waxy luster when polished, and distinct banding or inclusion patterns. Agate is found globally, notably in Brazil, India, and the United States (Lake Superior and Western states).