Rock Identifier
Fossilized Oyster Shell (Ostreidae (Calcium Carbonate - CaCO3)) — fossil
fossil

Fossilized Oyster Shell

Ostreidae (Calcium Carbonate - CaCO3)

Hardness: 3 on the Mohs scale (calcite/aragonite composition). Color: Grayish-white, beige, or brown. Luster: Pearly to dull earthy. Cleavage: None (layered shell structure). Specific Gravity: 2.7-2.9.

Hardness
3 on the Mohs scale (calcite/aragonite composition)
Color
Grayish-white, beige, or brown
Luster
Pearly to dull earthy
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Physical properties

Hardness: 3 on the Mohs scale (calcite/aragonite composition). Color: Grayish-white, beige, or brown. Luster: Pearly to dull earthy. Cleavage: None (layered shell structure). Specific Gravity: 2.7-2.9.

Formation & geological history

Formed through the accumulation and permineralization of marine bivalve oyster shells in shallow coastal ocean environments, typically dating from the Jurassic to the Pleistocene epochs.

Uses & applications

Used in educational collections, fossil display, historical coastal geology research, and crushed as a calcium additive in agriculture or aggregate.

Geological facts

Oysters have existed for over 250 million years. Giant fossil oysters like Gryphaea (Devil's Toenail) are famous index fossils used by geologists to date sedimentary rock layers.

Field identification & locations

Identified by its distinctive rough, layered, flaky structure reminiscent of modern marine oyster shells, but hardened and heavy due to fossilization. Commonly found in coastal sedimentary formations and limestone deposits.

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