mineral
Iron-rich jasper (likely brecciated jasper)
Jasper, microcrystalline quartz (SiO₂) colored by hematite/goethite and iron oxides
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque red-brown, black, and golden-brown coloration; vitreous to dull/waxy luster; cryptocrystalline quartz with no visible cleavage, commonly exhibiting conchoidal fracture. The specimen appears rough and iron-stained, possibly with brecciation or quartz-rich veins.
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Physical properties
Hardness about 6.5–7 Mohs; opaque red-brown, black, and golden-brown coloration; vitreous to dull/waxy luster; cryptocrystalline quartz with no visible cleavage, commonly exhibiting conchoidal fracture. The specimen appears rough and iron-stained, possibly with brecciation or quartz-rich veins.
Formation & geological history
Forms when silica-rich fluids cement or replace iron-rich sediments and volcanic material, often during hydrothermal activity or weathering; age depends on locality and may range from Precambrian to younger. Commonly associated with iron-formation and volcanic terrains.
Uses & applications
Used as ornamental stone, cabochons, beads, carvings, lapidary material, and occasionally decorative aggregate; attractive pieces have modest collector value.
Geological facts
Red coloration primarily reflects hematite, while yellow-brown areas may contain limonite or goethite. Jasper is technically a variety of chalcedony or microcrystalline quartz rather than a formal rock species.
Field identification & locations
Identify by its opaque red/black iron-oxide pattern, high hardness, lack of cleavage, and inability to scratch with a steel knife easily; a streak test is typically pale to reddish-brown. Common in Australia, India, Brazil, South Africa, and the western United States.
