mineral

Yellow chalcedony (likely tumbled quartz)

Chalcedony, microcrystalline quartz (SiO₂), colored by iron impurities

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, translucent to opaque, waxy or dull luster, yellow to honey-brown color, and no visible cleavage; conchoidal fracture and specific gravity about 2.6. The smooth rounded shape indicates tumbling or water abrasion.

Identified September 14, 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; yellow coloration commonly reflects iron oxides or hydroxides. Deposits range from ancient volcanic terrains to younger sedimentary environments.

Uses & applications

Used as a lapidary stone, cabochon, ornamental object, and inexpensive collector specimen; durable enough for beads and carvings. It is not generally used as a major construction aggregate in this form.

Geological facts

Chalcedony is quartz with crystals too small to see unaided; related varieties include agate, carnelian, chrysoprase, and jasper. Color boundaries or banding would suggest agate, while uniformly opaque material may be jasper.

Field identification & locations

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