mineral
Tumbled jasper or chert
Microcrystalline quartz (SiO₂), likely iron-stained jasper/chalcedony
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; brown, cream, and reddish mottling with a waxy to subvitreous luster, no visible crystal faces, and conchoidal fracture. The rounded shape indicates tumbling or natural abrasion.
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Physical properties
Hardness about 6.5–7 Mohs; brown, cream, and reddish mottling with a waxy to subvitreous luster, no visible crystal faces, and conchoidal fracture. The rounded shape indicates tumbling or natural abrasion.
Formation & geological history
Forms when silica-rich groundwater replaces or fills cavities in volcanic or sedimentary rocks, with iron oxides producing the brown-red colors. Most examples are geologically young relative to their host rocks, commonly Paleozoic–Cenozoic.
Uses & applications
Used for cabochons, beads, carvings, and inexpensive jewelry; larger jasper is also decorative stone. Common tumbled specimens generally have modest value.
Geological facts
Jasper is an opaque variety of chalcedony, whereas more translucent material is usually called agate or chalcedony. The image alone cannot reliably distinguish jasper from similarly colored chert or brecciated chalcedony.
Field identification & locations
Common worldwide, including India, Madagascar, Brazil, Mexico, the western United States, and Australia. Confirm with a hardness test against steel or glass, while avoiding damage to collectible pieces; it should not scratch quartz but can scratch glass.
