mineral
Tumbled red jasper
Microcrystalline quartz (chalcedony), predominantly SiO₂, colored by iron oxides
AI-generated identification · may be incorrectOpaque brick-red to deep brown with dark gray/black linear banding; dull to silky luster and no visible crystals. Mohs hardness 6.5–7, conchoidal fracture, massive cryptocrystalline structure, and specific gravity about 2.6.
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Physical properties
Opaque brick-red to deep brown with dark gray/black linear banding; dull to silky luster and no visible crystals. Mohs hardness 6.5–7, conchoidal fracture, massive cryptocrystalline structure, and specific gravity about 2.6.
Formation & geological history
Forms when silica-rich groundwater fills fractures, cavities, or replaces volcanic and sedimentary rock; iron oxides produce the red color. The pictured piece is polished/tumbled, so its precise geological age and locality cannot be determined.
Uses & applications
Used for cabochons, beads, carvings, paperweights, and lapidary specimens; historically used for tools and ornaments. It is durable but generally less valuable than translucent or vividly patterned agate.
Geological facts
The dark streaks may represent manganese/iron-rich layers or included host material, a common feature in banded jasper. Jasper is an opaque variety of chalcedony rather than a separately crystallized mineral species.
Field identification & locations
Identify it by its red opaque body, fine texture, hardness, and resistance to scratching by a steel blade; glass should not scratch it. Common sources include India, Madagascar, Brazil, Australia, and the western United States.
