mineral
Tumbled agate
Agate, a banded variety of microcrystalline quartz (SiO₂; chalcedony)
AI-generated identification · may be incorrectThe specimen is polished and reddish-brown, with a waxy to vitreous luster. Quartz hardness is 7 Mohs; crystals are microscopic and cleavage is absent. The image does not show diagnostic banding clearly.
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Physical properties
The specimen is polished and reddish-brown, with a waxy to vitreous luster. Quartz hardness is 7 Mohs; crystals are microscopic and cleavage is absent. The image does not show diagnostic banding clearly.
Formation & geological history
Agate forms as silica-rich fluids fill cavities in volcanic rock, depositing chalcedony in layers over time. Its age depends on its source deposit; agates commonly form in volcanic settings.
Uses & applications
Used for jewelry, ornaments, carvings, and inexpensive collector specimens; agate is also used in precision components and abrasives.
Geological facts
Agate’s characteristic bands can reveal successive stages of mineral deposition, though some varieties have little visible banding.
Field identification & locations
Look for hardness, waxy luster, and translucent edges; banding is a useful clue, but this polished piece cannot be identified definitively from appearance alone. Agates occur worldwide, including Brazil, Uruguay, India, and the western United States.
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