mineral
Tumbled jasper (likely brecciated or ocean jasper)
Microcrystalline quartz (SiO₂), with iron-oxide staining and possible chalcedony
AI-generated identification · may be incorrectOpaque reddish-brown to mustard specimen with rounded polished surfaces, mottled pattern, and small cavities; vitreous to dull luster. Quartz hardness is about 6.5–7 Mohs; no visible cleavage, with conchoidal fracture and specific gravity near 2.6.
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Physical properties
Opaque reddish-brown to mustard specimen with rounded polished surfaces, mottled pattern, and small cavities; vitreous to dull luster. Quartz hardness is about 6.5–7 Mohs; no visible cleavage, with conchoidal fracture and specific gravity near 2.6.
Formation & geological history
Formed when silica-rich fluids filled or replaced volcanic cavities and fractures, with iron oxides producing the red-brown coloration; likely Cenozoic volcanic material. The surface has been human-tumbled and polished.
Uses & applications
Used for cabochons, beads, carvings, ornamental objects, and lapidary collections; too small and irregular for construction use.
Geological facts
Jasper is an opaque variety of microcrystalline quartz, commonly classified as a gemstone or lapidary material rather than a formal rock type. Exact variety cannot be confirmed from the photograph alone.
Field identification & locations
Identify by its opaque body, waxy-to-glassy polish, quartz-like hardness, and inability to scratch with a steel knife; it should not fizz in dilute acid. Common sources include Madagascar, Indonesia, Brazil, India, and the western United States.
