mineral

Polished pink agate/chalcedony pebble

Chalcedony (microcrystalline quartz, SiO₂), likely iron-stained agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; pale pink to reddish-brown with cloudy, possibly faintly banded zones; waxy to vitreous luster; cryptocrystalline quartz with no cleavage and conchoidal fracture. Specific gravity is about 2.6.

Identified August 27, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, often developing concentric bands; iron oxides create the red-brown coloration. Exact age depends on its host rock, commonly Paleozoic–Cenozoic.

Uses & applications

Used for cabochons, beads, carvings, tumbling, ornaments, and small decorative objects; polished pieces have modest lapidary value.

Geological facts

Agate is a variety of chalcedony distinguished by banding or patterned internal zoning, though some specimens are nearly opaque and weakly banded.

Field identification & locations

Identify it by its very hard, smooth surface, waxy polish, translucent edges, and resistance to scratching by steel; it should scratch glass but not be scratched by a knife. Common sources include Brazil, Uruguay, India, Mexico, Madagascar, and the western United States.