mineral

Polished yellow-brown agate or chalcedony

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony/agate

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent honey-yellow to brown with milky areas, waxy-to-glassy luster, and conchoidal fracture. Quartz has trigonal crystal structure, though microscopic crystals are not individually visible; no cleavage and specific gravity about 2.6.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Formed when silica-rich groundwater filled cavities or fractures in volcanic rock, later colored by iron-oxide impurities. The specimen’s exact geological age cannot be determined visually; agates commonly range from Paleozoic to Cenozoic.

Uses & applications

Used as ornamental stone, cabochons, carvings, beads, and lapidary pieces; polished material is mainly collectible or decorative rather than structural.

Geological facts

The irregular cream, amber, and brown patterning is typical of chalcedony with iron staining, but distinct banding is not obvious enough to confirm classic agate.

Field identification & locations

Commonly found in volcanic terrains, especially Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. Field identification relies on waxy translucency, hardness, conchoidal fracture, and inability to scratch it with a steel knife; confirm with specific-gravity or quartz testing.