mineral

Tumbled chalcedony (likely pale agate or quartz)

Microcrystalline quartz, SiO₂ (chalcedony; possibly quartz-rich agate)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; creamy white to honey-yellow, translucent, with a waxy to vitreous luster and no visible cleavage. Its rounded, polished form obscures crystal structure; specific gravity is about 2.6.

Identified August 26, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, precipitating microscopic quartz fibers over long periods, commonly during the Cenozoic or older. The specimen has been mechanically tumbled and polished.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and lapidary practice; attractive banded agate varieties are used in jewelry and collectibles.

Geological facts

Chalcedony is quartz that crystallized too finely to show obvious individual crystals. Yellow coloration may result from iron staining or included iron minerals.

Field identification & locations

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