mineral
Tumbled brown agate
Microcrystalline quartz (SiO₂), variety of chalcedony
AI-generated identification · may be incorrectMohs hardness 6.5–7; brown, translucent to opaque with a waxy-to-glassy luster and no visible cleavage. Agate has a cryptocrystalline quartz structure; this small tumbled piece shows no clear banding.
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Physical properties
Mohs hardness 6.5–7; brown, translucent to opaque with a waxy-to-glassy luster and no visible cleavage. Agate has a cryptocrystalline quartz structure; this small tumbled piece shows no clear banding.
Formation & geological history
Forms as silica-rich fluid fills cavities in volcanic rock, depositing successive layers of chalcedony; agates occur in rocks of many ages. The polished shape is human-finished.
Uses & applications
Used for jewelry, ornaments, and lapidary collections; agate is also used in small precision components because it is hard and takes a smooth polish.
Geological facts
Agate is a banded form of chalcedony, although banding may be subtle or absent in individual pieces.
Field identification & locations
Look for hardness, waxy luster, and any translucent edges or fine internal bands; common sources include Brazil, Uruguay, India, and the United States. The image alone cannot confirm the exact variety.
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