Rock Identifier
Fossil shell fragment (Indeterminate molluscan bioclast, likely aragonite or calcite) — fossil
fossil

Fossil shell fragment

Indeterminate molluscan bioclast, likely aragonite or calcite

AI-generated identification · may be incorrect

Cream to pale orange, irregularly triangular fragment with faint layered shell texture; hardness typically 3–4 (calcite) or about 3.5–4 (aragonite), vitreous to dull luster, and no obvious cleavage. Specific gravity is approximately 2.6–2.9.

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Physical properties

Cream to pale orange, irregularly triangular fragment with faint layered shell texture; hardness typically 3–4 (calcite) or about 3.5–4 (aragonite), vitreous to dull luster, and no obvious cleavage. Specific gravity is approximately 2.6–2.9.

Formation & geological history

A biological shell formed in a marine or freshwater environment, then fragmented and preserved in sediment; its age cannot be determined from the image and may range from recent to fossiliferous Mesozoic or Cenozoic material.

Uses & applications

Used mainly for collecting, education, jewelry, and decorative crafts; carbonate shell material may also be processed into lime or calcium supplements.

Geological facts

The visible curved growth layers are consistent with shell architecture rather than an igneous or metamorphic texture. Acid testing can distinguish carbonate: calcite effervesces strongly in dilute hydrochloric acid, while aragonite also reacts but may be less stable.

Field identification & locations

Likely found in beaches, limestone, shell beds, or sedimentary deposits. Examine both surfaces for growth lines, hinge or rib features; avoid destructive testing unless permitted.

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