mineral

Tumbled chalcedony (likely carnelian/cream agate)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide staining

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; creamy white to honey-brown with translucent edges and rusty inclusions. Waxy to vitreous luster, cryptocrystalline structure, no cleavage, conchoidal fracture; specific gravity about 2.60.

Identified August 23, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, later colored by iron oxides; commonly Cenozoic to older. This specimen has been mechanically tumbled and polished.

Uses & applications

Used for beads, cabochons, carvings, and ornamental objects; attractive material is inexpensive but popular with collectors.

Geological facts

Chalcedony is quartz whose crystals are too small to see without magnification; color zoning and iron staining can produce agate or carnelian-like varieties.

Field identification & locations

Identify by its smooth waxy surface, translucency, quartz hardness, and lack of cleavage; it should scratch glass but not be scratched by a steel knife. Common in volcanic terrains worldwide, including Brazil, India, Madagascar, Uruguay, and the western United States.