mineral
Tumbled brown agate or jasper pebble
Microcrystalline quartz, chiefly chalcedony (SiO₂), possibly iron-stained jasper
AI-generated identification · may be incorrectSmooth, rounded, opaque to slightly translucent brown specimen with a waxy luster and small cream-colored mineral-filled pits. Hardness about 6.5–7 Mohs; trigonal quartz structure, no cleavage, conchoidal fracture; specific gravity approximately 2.6.
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Physical properties
Smooth, rounded, opaque to slightly translucent brown specimen with a waxy luster and small cream-colored mineral-filled pits. Hardness about 6.5–7 Mohs; trigonal quartz structure, no cleavage, conchoidal fracture; specific gravity approximately 2.6.
Formation & geological history
Likely formed when silica-rich groundwater filled cavities or replaced host rock, with iron oxides producing the brown color; later naturally or artificially tumbled. Agate and jasper commonly formed in volcanic rocks from Paleozoic to Cenozoic environments.
Uses & applications
Used as a decorative pebble, lapidary material, cabochon, bead, or inexpensive jewelry stone; polished pieces are also collected.
Geological facts
Agate is translucent and commonly banded, whereas jasper is opaque and more uniformly colored; this specimen may be an iron-rich jasper or brown chalcedony rather than confidently identifiable agate.
Field identification & locations
Look for waxy luster, very smooth conchoidal surfaces, absence of cleavage, and inability to scratch it with a steel knife; quartz should scratch glass. Common worldwide in volcanic terrains and gravel deposits.
