mineral
Tumbled brown agate
Microcrystalline quartz (SiO₂), a banded variety of chalcedony
AI-generated identification · may be incorrectMohs hardness 6.5–7; brown and translucent to opaque, with a waxy-to-vitreous luster and subtle parallel banding. Agate is cryptocrystalline and has no visible cleavage; the surface appears polished or tumbled.
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Physical properties
Mohs hardness 6.5–7; brown and translucent to opaque, with a waxy-to-vitreous luster and subtle parallel banding. Agate is cryptocrystalline and has no visible cleavage; the surface appears polished or tumbled.
Formation & geological history
Forms as silica-rich groundwater deposits chalcedony in cavities, commonly in volcanic rocks; the pictured stone cannot be dated from appearance alone.
Uses & applications
Used for jewelry, carvings, ornaments, and collections; agate is also used for small decorative objects and, historically, precision components.
Geological facts
Agate’s fine quartz fibers can produce distinctive curved or concentric bands, though banding may be faint or hidden in a small tumbled piece.
Field identification & locations
Look for waxy translucence and curved bands; agate occurs worldwide, especially in volcanic regions and alluvial gravels. The photo suggests agate, but identification is not definitive without closer inspection.
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