sedimentary
Fossiliferous Limestone (Bivalve Fossil)
Calcium Carbonate (CaCO3) with Bivalvia fossil
Hardness: 3 (Mohs scale), Color: Cream/Tan/Grey, Luster: Dull or earthy, Structure: Bioclastic/Fine-grained matrix, Cleavage: None (fractures irregularly)
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Physical properties
Hardness: 3 (Mohs scale), Color: Cream/Tan/Grey, Luster: Dull or earthy, Structure: Bioclastic/Fine-grained matrix, Cleavage: None (fractures irregularly)
Formation & geological history
Formed in shallow marine environments where skeletal debris or shells (like the bivalve shown) accumulate and are compressed over millions of years. Most common in Paleozoic to Cenozoic strata.
Uses & applications
Used primarily in the construction industry as crushed stone, for making cement, or as agricultural lime. Fossiliferous pieces are popular in geological collections and as educational tools.
Geological facts
Limestone often makes up about 10% of the total volume of all sedimentary rocks. The specific specimen shown appears to be a cast or partial shell of a bivalve, a class of marine mollusks that includes clams and oysters.
Field identification & locations
Identify in the field by searching for circular or shell-shaped indentations in soft, light-colored rocks. It will fizz when exposed to a drop of weak acid (vinegar or hydrochloric acid). Found commonly in areas that were once prehistoric seafloors.
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