mineral
Likely tumbled brown agate
Microcrystalline quartz (SiO₂), a variety of chalcedony
AI-generated identification · may be incorrectSmall, polished dark-brown pebble with possible lighter banding; quartz hardness 6.5–7 Mohs, vitreous to waxy luster, and no visible cleavage. The image is not detailed enough to confirm banding or identify the exact variety.
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Physical properties
Small, polished dark-brown pebble with possible lighter banding; quartz hardness 6.5–7 Mohs, vitreous to waxy luster, and no visible cleavage. The image is not detailed enough to confirm banding or identify the exact variety.
Formation & geological history
Agate forms as silica-rich fluids fill cavities in volcanic rocks and deposit layers of chalcedony; deposits span many geological ages. This specimen appears mechanically tumbled and polished.
Uses & applications
Used for jewelry, beads, ornaments, and collecting; agate is also used for decorative objects and, historically, precision instruments.
Geological facts
Agate is valued for its layered patterns, which can reveal successive episodes of mineral deposition.
Field identification & locations
Look for translucency at thin edges and curved or parallel bands; hardness and appearance alone cannot confirm agate from this photo. Agates occur worldwide, notably in Brazil, Uruguay, India, and the United States.
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