mineral

Tumbled white chalcedony (milky agate)

Microcrystalline quartz, SiO₂; chalcedony, locally grading toward milky agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent white to cream with faint honey or gray zones, waxy-to-glassy luster, cryptocrystalline structure, and no visible cleavage. Specific gravity is approximately 2.6.

Identified August 10, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; translucent white to cream with faint honey or gray zones, waxy-to-glassy luster, cryptocrystalline structure, and no visible cleavage. Specific gravity is approximately 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, depositing microscopic quartz fibers in volcanic rocks; specimens commonly formed during the Cenozoic or older depending on the source. The rounded shape and polish are human-produced.

Uses & applications

Used as a lapidary stone, worry stone, cabochon, bead, and inexpensive jewelry or decor material. It is valued mainly for translucency, pattern, polish, and smoothness.

Geological facts

Chalcedony is quartz too fine-grained for individual crystals to be seen; colorless or white varieties are often marketed as milky agate or white agate.

Field identification & locations

Identify by its cool, glassy/waxy feel, strong polish, lack of cleavage, and ability to scratch steel or glass; it should not fizz in dilute acid. Common sources include Brazil, Uruguay, India, Madagascar, and the western United States.