mineral

Banded agate fragment

Agate, microcrystalline quartz (SiO₂), commonly with chalcedony and iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent honey-brown, cream, and gray banding; waxy to vitreous luster; cryptocrystalline quartz with no cleavage and conchoidal fracture. The sharp faces suggest a broken or roughly cut fragment.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony and quartz in successive bands; individual agates may range from Paleozoic to recent age. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.

Uses & applications

Used for cabochons, beads, carvings, bookends, and decorative objects; small rough fragments have modest specimen value.

Geological facts

The curved color bands reflect changing chemistry during cavity filling, while brown coloration commonly comes from iron oxides or hydroxides.

Field identification & locations

Identify by curved or concentric banding, translucent edges, waxy surface, and glass-like conchoidal fracture; it should resist scratching by a steel knife. This specimen’s appearance is consistent with agate, though exact identification would benefit from a polished surface or locality information.