mineral
Green tumbled agate (likely green chalcedony)
Chalcedony, microcrystalline quartz (SiO₂); exact identification is uncertain from the photo
AI-generated identification · may be incorrectSmooth, opaque-to-translucent dark-green pebble with a waxy to vitreous luster. Quartz hardness is about 6.5–7 Mohs; crystals are microscopic and no cleavage is visible.
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Physical properties
Smooth, opaque-to-translucent dark-green pebble with a waxy to vitreous luster. Quartz hardness is about 6.5–7 Mohs; crystals are microscopic and no cleavage is visible.
Formation & geological history
Forms when silica-rich fluids deposit quartz in cavities or fractures, commonly in volcanic rocks; the specimen has been tumbled and may be dyed. Geological age cannot be determined from appearance.
Uses & applications
Used for inexpensive jewelry, beads, cabochons, and decorative pieces; agate is also collected and used for ornaments.
Geological facts
Agate is a banded variety of chalcedony, though bands are not apparent on this small polished piece.
Field identification & locations
Look for fine banding, translucency at thin edges, and hardness sufficient to scratch glass; vivid, uniform green color may indicate treatment. Chalcedony occurs worldwide, including Brazil, India, Uruguay, and the United States.
