mineral

Banded agate (likely carnelian–chalcedony agate)

Microcrystalline quartz, SiO₂ (chalcedony with iron-oxide bands)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent white, gray, red, and brown bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage, conchoidal fracture; specific gravity about 2.6.

Identified August 18, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; translucent white, gray, red, and brown bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage, conchoidal fracture; specific gravity about 2.6.

Formation & geological history

Forms when silica-rich groundwater repeatedly fills cavities in volcanic rock, depositing chalcedony and iron-stained layers. Most agates formed during the Cenozoic or older volcanic episodes, depending on locality.

Uses & applications

Used for cabochons, carvings, bookends, slabs, and ornamental objects; attractive banding gives it modest collector value.

Geological facts

The red coloration is generally caused by hematite or goethite; alternating bands record changes in fluid chemistry during cavity filling.

Field identification & locations

Identify by curved or parallel chalcedony banding, glassy edges, hardness, and conchoidal fracture; it commonly occurs in basaltic volcanic provinces worldwide. A locality label is needed for precise identification.