mineral

Banded agate geode fragment

Cryptocrystalline quartz (chalcedony), SiO₂, with an inner botryoidal or drusy quartz cavity

AI-generated identification · may be incorrect

Typically hardness 6.5–7 Mohs, waxy to vitreous luster, gray-white concentric banding, and conchoidal fracture; the rounded cavity lining is likely microcrystalline quartz. Specific gravity is about 2.58–2.64.

Identified August 13, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited successive chalcedony layers in a vesicle or cavity, later leaving a quartz-lined void. The exact geological age and locality cannot be determined from the image alone; agates commonly form in volcanic rocks from Paleozoic to Cenozoic settings.

Uses & applications

Used as lapidary rough, cabochons, jewelry, carvings, and collectible geodes; small fragments generally have modest commercial value.

Geological facts

The layered bands record repeated changes in fluid chemistry and silica deposition. The white rounded forms may be botryoidal chalcedony rather than individual large crystals.

Field identification & locations

Identify by fine concentric banding, translucent chalcedony, quartz hardness, and lack of cleavage; it may be found in basaltic volcanic terrains and alluvial gravels. A locality label or testing for quartz would improve identification.