mineral
Polished pink agate/chalcedony pebble
Chalcedony (microcrystalline quartz, SiO₂), likely iron-stained agate
AI-generated identification · may be incorrectHardness 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.
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Physical properties
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.
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.
