mineral
Polished/tumbled agate or jasper
Cryptocrystalline quartz, SiO₂; likely mossy or dendritic agate/jasper variety
AI-generated identification · may be incorrectDark olive-brown, gray, and translucent zones with a glassy-to-waxy luster; massive microcrystalline quartz, no visible cleavage, Mohs hardness 6.5–7, specific gravity about 2.6. The rounded shape is human-polished.
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Physical properties
Dark olive-brown, gray, and translucent zones with a glassy-to-waxy luster; massive microcrystalline quartz, no visible cleavage, Mohs hardness 6.5–7, specific gravity about 2.6. The rounded shape is human-polished.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, depositing chalcedony and iron/manganese impurities in bands or cloudy zones. Agates commonly formed during volcanic activity from the Precambrian through Cenozoic, depending on locality.
Uses & applications
Used for cabochons, beads, carvings, paperweights, and lapidary specimens; durable varieties are also used for ornaments and small industrial components.
Geological facts
The image is too blurred for a definitive variety; the opaque dark areas may make it jasper rather than true agate. Internal color patterns arise from trace iron and other mineral inclusions.
Field identification & locations
Identify by its quartz-like hardness, smooth waxy/glassy surface, conchoidal fracture if broken, and lack of cleavage; common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.
