sedimentary

Fossiliferous Limestone (Coquina / Shell Limestone Egg)

Biogenic Limestone (composed primarily of Calcite, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Cream, beige, tan, and light brown with white fossil shell fragments; Luster: Vitreous to dull (polished to high gloss here); Structure: Fine-grained matrix embedded with fossilized mollusks/bivalve shells; Specific Gravity: ~2.5 - 2.7.

Hardness: 3 on Mohs scale
Luster: Vitreous to dull (polished to high gloss here)

Identified October 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in warm, shallow marine environments through the accumulation and compaction of broken shell fragments and skeletal debris of marine organisms over millions of years, cemented by calcium carbonate.

Uses & applications

Commonly carved and polished into decorative shapes such as eggs, spheres, and bookends; used in architectural stones, tiles, counter surfaces, and collected as ornamental fossil specimens.

Geological facts

Fossiliferous limestones often preserve cross-sections of ancient marine life such as brachiopods, gastropods, and bivalves. When carved and polished, these cross-sections reveal beautiful natural curved spiral and shell-wall patterns.

Field identification & locations

Identified by visible shell cross-sections embedded in a carbonate matrix and a positive effervescence reaction to weak acid (hydrochloric acid/vinegar). Widely sourced globally, including Morocco, Europe, and North America.