mineral

Tumbled yellow chalcedony (likely yellow agate)

Chalcedony, microcrystalline quartz (SiO₂); possibly iron-stained agate

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, waxy to vitreous luster, translucent yellow to honey coloration, and no visible cleavage; cryptocrystalline quartz has microscopic interlocking fibers. The rounded shape and polish indicate human tumbling.

Identified September 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities or fractures, precipitating microcrystalline quartz; yellow coloration commonly results from iron oxides or hydroxides. Chalcedony deposits range from ancient volcanic cavities to younger hydrothermal and sedimentary environments.

Uses & applications

Used as a lapidary stone for cabochons, beads, carvings, and decorative objects; durable enough for jewelry but less valuable than fine transparent gemstones.

Geological facts

Agate is banded or patterned chalcedony, while uniformly colored material is generally called chalcedony or jasper depending on opacity. This specimen’s internal cloudy zones and brown fracture staining are consistent with iron-bearing chalcedony.

Field identification & locations

Identify by its waxy appearance, translucency, lack of cleavage, and ability to scratch ordinary glass; it should not fizz in dilute acid. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.