mineral

Tumbled chalcedony pebble

Microcrystalline quartz (SiO₂), likely ferruginous or jasper-like chalcedony

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent tan, cream, and reddish-brown coloration with a waxy to dull luster. Quartz has a trigonal crystal structure, no cleavage, and specific gravity near 2.60–2.65; the rounded surface indicates tumbling or natural water wear.

Identified September 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, precipitating microscopic quartz fibers; iron impurities create the brown-red patches. Chalcedony commonly forms in volcanic rocks, generally from Paleozoic to Cenozoic settings, though its exact age cannot be determined visually.

Uses & applications

Used for cabochons, beads, carvings, lapidary material, and decorative polished stones; this small ordinary specimen has modest commercial value.

Geological facts

The visible cloudy, fine-grained texture distinguishes chalcedony from transparent crystalline quartz. Red-brown areas may qualify as jasper if sufficiently opaque and iron-rich.

Field identification & locations

Identify by its very fine texture, waxy appearance, quartz-like hardness, lack of cleavage, and inability to scratch with a steel knife easily; common in volcanic terrains, river gravels, and alluvial deposits worldwide.