mineral
Tumbled red jasper and related pebbles
Jasper, a microcrystalline variety of quartz (SiO₂), commonly containing hematite/goethite and other iron oxides
AI-generated identification · may be incorrectOpaque reddish-brown to maroon, earthy to vitreous luster, quartz microcrystals, no visible cleavage, conchoidal fracture; Mohs hardness about 6.5–7 and specific gravity roughly 2.5–2.7. The pieces appear rounded and polished/tumbled, with some darker possibly basaltic or iron-rich fragments.
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Physical properties
Opaque reddish-brown to maroon, earthy to vitreous luster, quartz microcrystals, no visible cleavage, conchoidal fracture; Mohs hardness about 6.5–7 and specific gravity roughly 2.5–2.7. The pieces appear rounded and polished/tumbled, with some darker possibly basaltic or iron-rich fragments.
Formation & geological history
Jasper forms when silica-rich fluids replace or cement volcanic ash, sediment, or other rock, with iron oxides producing the red coloration. Deposits occur in many ages, from Precambrian iron-formations to younger volcanic and sedimentary settings.
Uses & applications
Used for cabochons, beads, carvings, ornaments, lapidary rough, and decorative stone; occasionally as aggregate or facing stone. Common tumbled pieces have modest commercial value.
Geological facts
Color intensity reflects finely dispersed iron oxides rather than large visible crystals. Jasper is cryptocrystalline quartz and is often difficult to distinguish visually from red chert or heavily iron-stained volcanic rock.
Field identification & locations
Identify by its opaque red-brown color, very hard glassy edges, lack of cleavage, and inability to scratch it with a steel knife easily; it should scratch glass. Common locations include India, Madagascar, Brazil, South Africa, Australia, and the western United States.
