sedimentary
Banded Agate / Shell Fossil Fragment
Silicon Dioxide (SiO2) / Calcium Carbonate (CaCO3)
Hardness 6.5-7 (if agate) or 3-3.5 (if shell fragment). Light tan, beige, and white translucent concentric banding. Vitreous to waxy luster, smooth beach-tumbled texture.
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Physical properties
Hardness 6.5-7 (if agate) or 3-3.5 (if shell fragment). Light tan, beige, and white translucent concentric banding. Vitreous to waxy luster, smooth beach-tumbled texture.
Formation & geological history
Formed either through silica deposition filling cavities in volcanic or sedimentary rocks, or as a water-worn fragment of a marine mollusk shell composed of aragonite/calcite.
Uses & applications
Beachcombing collectible, lapidary art, wire-wrapping jewelry, or decorative tumbling stone.
Geological facts
Water-worn fragments on beaches can be easily confused between chalcedony/agate pebbles and thick bivalve shell fragments due to identical concentric growth or depositional lines.
Field identification & locations
Identified by parallel concentric bands and rounded smooth edges from wave action. Common along marine beaches, lakeshores, and river beds worldwide.
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