mineral

Banded Agate

Chalcedony / Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, grey, white bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture.

Hardness: 6
Color: Brown, grey, white bands
Luster: Waxy to vitreous

Identified May 7, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, grey, white bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture.

Formation & geological history

Formed primarily in volcanic rock cavities (vesicles) or metamorphic rocks where silica-rich groundwater deposits layers of microcrystalline quartz over long periods of time.

Uses & applications

Used extensively in jewelry, ornamental carvings, lapidary art, and industrial components like precision scale bearings and mortars/pestles.

Geological facts

The distinct internal banding is known as 'chalcedony' and is created by rhythmic crystallization. This specimen specifically shows 'waterline' or 'onyx' banding, indicating it formed with a consistent gravitational orientation.

Field identification & locations

Identify by its translucent nature, distinctive concentric or parallel banding, and smooth waxy texture when polished. Commonly found in Brazil, Uruguay, and various volcanic regions worldwide.