mineral

Tumbled gray-green chalcedony

Microcrystalline quartz (SiO₂), likely chalcedony or quartz-rich river pebble

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque to slightly translucent, gray-green to brown, with a waxy luster and rounded, smoothly worn surface. Quartz has a trigonal crystal structure but is cryptocrystalline here; cleavage is absent and specific gravity is about 2.6.

Identified August 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed from silica-rich groundwater filling cavities or replacing rock, or produced as a naturally rounded stream pebble; its exact geological age and locality cannot be determined from the photograph.

Uses & applications

Used for beads, carvings, cabochons, tumbling, and decorative objects; lower-grade material has limited industrial value as silica aggregate.

Geological facts

The subdued waxy appearance and lack of visible crystals are typical of chalcedony, though similar-looking jasper, chert, and weathered quartz are possible.

Field identification & locations

Test with a steel file or glass only cautiously: genuine chalcedony can scratch glass, while a knife generally cannot scratch it. Common sources include Brazil, Uruguay, India, Madagascar, and many river gravels; exact identification may require specific-gravity or microscopic testing.