sedimentary
Fossilized Shell in Limestone
Bivalve fossil (CaCO3) in Carbonate Sedimentary Rock
Hardness: 3-4 (Mohs), Color: Light gray to tan with darker carbonaceous streaks, Luster: Dull/Earthy, Crystal Structure: Microcrystalline calcite with organic preservation, Cleavage: None/Irregular
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Physical properties
Hardness: 3-4 (Mohs), Color: Light gray to tan with darker carbonaceous streaks, Luster: Dull/Earthy, Crystal Structure: Microcrystalline calcite with organic preservation, Cleavage: None/Irregular
Formation & geological history
Formed by the accumulation of organic debris and calcium carbonate shells in a shallow marine environment over millions of years, typically during the Paleozoic or Mesozoic eras.
Uses & applications
Primarily used in construction (countertops, tiling), as a source of lime, and for paleontological study or decorative fossil collecting.
Geological facts
The shell visible is a bivalve, a member of the class of mollusks that includes clams and oysters. Fossils provide a snapshot of prehistoric marine ecosystems.
Field identification & locations
Identify in the field by looking for concentric growth rings on embedded shapes and the presence of calcite veining or reaction to dilute hydrochloric acid. Common in ancient seabed outcrops.
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