mineral
Red chalcedony (likely dyed or heat-treated)
Microcrystalline quartz, SiO₂; possibly red agate/carnelian
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent red-orange, waxy to vitreous luster, cryptocrystalline quartz, no cleavage, conchoidal fracture, specific gravity about 2.6. The rough, glossy appearance and uniform vivid color may indicate polishing, dyeing, or treatment.
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Physical properties
Hardness 6.5–7 Mohs; translucent red-orange, waxy to vitreous luster, cryptocrystalline quartz, no cleavage, conchoidal fracture, specific gravity about 2.6. The rough, glossy appearance and uniform vivid color may indicate polishing, dyeing, or treatment.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly during the Cenozoic or older volcanic episodes. Red color generally comes from iron oxides or artificial treatment.
Uses & applications
Used for cabochons, beads, carvings, ornaments, and small decorative specimens; poorer material is used in inexpensive lapidary work.
Geological facts
Carnelian is the orange-red variety of chalcedony, while red agate commonly shows banding; this specimen appears largely unbanded. Identification should be confirmed with a hardness, magnification, and dye-penetration test.
Field identification & locations
Common in Brazil, Uruguay, India, Madagascar, Mexico, and the United States. It should scratch glass but not be scratched by a steel knife; natural agate often shows bands or color variation.
