mineral
Tumbled brown chalcedony or jasper pebble
Microcrystalline quartz, SiO₂; possibly iron-rich jasper
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; brown to reddish-brown, opaque to weakly translucent, with a waxy-to-dull luster and no visible cleavage. The rounded shape and surface polish indicate natural tumbling or water wear.
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Physical properties
Hardness about 6.5–7 Mohs; brown to reddish-brown, opaque to weakly translucent, with a waxy-to-dull luster and no visible cleavage. The rounded shape and surface polish indicate natural tumbling or water wear.
Formation & geological history
Forms when silica-rich groundwater fills cavities or fractures, with iron oxides producing the brown-red color; jasper varieties may originate in volcanic or sedimentary settings. Exact geological age cannot be determined visually.
Uses & applications
Used as a tumbled collectible, cabochon, bead, or lapidary material; larger jasper pieces are also used decoratively. Common specimens generally have modest commercial value.
Geological facts
Chalcedony is quartz composed of microscopic intergrowths, while jasper is its opaque, impurity-rich variety. Brown color commonly reflects hematite or limonite inclusions.
Field identification & locations
Identify by its glassy/waxy appearance, lack of cleavage, rounded fracture, and ability to scratch ordinary glass; it should not fizz in dilute acid. Common in gravels and silica-rich volcanic or sedimentary deposits worldwide.
