mineral
Tumbled brown agate (probable)
Microcrystalline quartz, SiO₂ (chalcedony/agate)
AI-generated identification · may be incorrectTypically Mohs hardness 6.5–7, waxy to vitreous luster, brown to black banding or inclusions, and no visible cleavage; polished surfaces are rounded and glossy. The dark markings could also reflect iron/manganese-rich dendrites or another included mineral.
Identified More mineral →
Explore Tumbled brown agate (probable) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically Mohs hardness 6.5–7, waxy to vitreous luster, brown to black banding or inclusions, and no visible cleavage; polished surfaces are rounded and glossy. The dark markings could also reflect iron/manganese-rich dendrites or another included mineral.
Formation & geological history
Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in successive layers over millions of years. Common source rocks are ancient basaltic lavas and volcanic geodes.
Uses & applications
Used for cabochons, beads, carvings, bookends, and lapidary collections; its toughness makes it suitable for polished decorative objects.
Geological facts
Agate is a variety of chalcedony rather than a separate mineral species, and its banding records changing chemistry during cavity filling.
Field identification & locations
Identify by its glassy/waxy polish, hardness, translucency at thin edges, and cryptocrystalline banding; common localities include Brazil, Uruguay, India, Mexico, and the United States. A definitive identification would require observing the interior or testing hardness and specific gravity.
