mineral

Orange-brown chalcedony / agate rough

Microcrystalline quartz, SiO₂ (chalcedony, locally agate); possibly iron-oxide stained

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, translucent gray, honey-orange, brown, and reddish colors, with waxy to vitreous luster and conchoidal fracture; quartz has trigonal crystal structure but is cryptocrystalline here. No obvious cleavage; specific gravity is about 2.6.

Identified August 24, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities, fractures, or vesicles in volcanic rock and precipitates layer by layer; iron oxides create the orange-red staining. The specimen’s exact geological age cannot be determined from the image and depends on its host formation.

Uses & applications

Used for cabochons, beads, carvings, polished slabs, and decorative stone; large rough pieces are primarily collector or display specimens.

Geological facts

The translucent, waxy appearance and irregular color zoning are typical of chalcedony, while distinct curved bands would support the name agate. White areas may be quartz, calcite, or weathered matrix and require testing.

Field identification & locations

Commonly found in volcanic terrains, especially Brazil, Uruguay, Mexico, India, Madagascar, and the western United States; test with a steel file or quartz reference, though avoid damaging display pieces. Estimated value: $10–$100 for common rough material, or $100–$500+ for unusually large, colorful, polishable specimens.