sedimentary

Fossiliferous Limestone (Bivalve Fossil)

Calcium Carbonate (CaCO3) with Bivalvia fossil

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale), Color: Cream/Tan/Grey, Luster: Dull or earthy, Structure: Bioclastic/Fine-grained matrix, Cleavage: None (fractures irregularly)

Identified April 7, 2026More sedimentary →

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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.