igneous
Rhyolitic jasper / brecciated jasper
Silica-rich volcanic rock, chiefly microcrystalline quartz (SiO₂), with iron-oxide and clay/mineral impurities
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; mottled salmon-red, gray, cream, and brown; opaque with dull to waxy luster. The visible angular color patches suggest brecciation, while silica-filled areas are cryptocrystalline rather than visibly crystalline.
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Physical properties
Hardness about 6.5–7 Mohs; mottled salmon-red, gray, cream, and brown; opaque with dull to waxy luster. The visible angular color patches suggest brecciation, while silica-filled areas are cryptocrystalline rather than visibly crystalline.
Formation & geological history
Likely formed from silica-rich volcanic lava or volcanic ash that cooled and later underwent fracturing and silica-rich fluid alteration; iron oxides produced the red coloration. Exact geological age cannot be determined from the photograph.
Uses & applications
Used as ornamental stone, cabochons, carvings, polished slabs, and lapidary material; occasionally collected as a decorative volcanic specimen.
Geological facts
Jasper is technically a variety of opaque, impure chalcedony or microcrystalline quartz; “rhyolitic jasper” is a common lapidary description rather than a strict mineral species.
Field identification & locations
Identify by its opacity, very fine texture, red iron-stained patches, and quartz-like hardness; it should resist scratching by a steel knife. Similar material occurs in volcanic regions worldwide, including the western United States, Mexico, Australia, and Madagascar.
