mineral
Tumbled brown agate
Microcrystalline quartz (SiO₂), a variety of chalcedony
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; reddish- to dark-brown, with a smooth polished surface and waxy to vitreous luster. Agate typically has cryptocrystalline quartz and may show banding, though none is clearly visible here.
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Physical properties
Hardness 6.5–7 Mohs; reddish- to dark-brown, with a smooth polished surface and waxy to vitreous luster. Agate typically has cryptocrystalline quartz and may show banding, though none is clearly visible here.
Formation & geological history
Forms as silica-rich fluid deposits in cavities, commonly in volcanic rocks; its bands develop through successive mineral deposition. Agates occur in rocks of many geological ages.
Uses & applications
Used for jewelry, beads, ornaments, and lapidary collections; agate is also used in some precision and decorative applications.
Geological facts
Agate is a chalcedony variety, not a separate mineral species; tumbling smooths its natural surface and can make subtle patterns harder to see.
Field identification & locations
The small, rounded, polished brown specimen is consistent with tumbled agate, but the image alone cannot confirm its identity. Common sources include Brazil, Uruguay, India, and the United States.
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