sedimentary

Fossiliferous Limestone with Crinoid Stem fragment

Calcite (CaCO3) containing Crinoidea fossils

AI-generated identification · may be incorrect

Hardness: 3 (Mohs); Color: Gray to light tan; Luster: Dull/Earthy; Crystal structure: Trigonal/Hexagonal (calcite matrix); Cleavage: Perfect rhombohedral in calcite matrix; Specific gravity: 2.71

Hardness: 3 (Mohs)
Color: Gray to light tan
Luster: Dull/Earthy

Identified June 3, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs); Color: Gray to light tan; Luster: Dull/Earthy; Crystal structure: Trigonal/Hexagonal (calcite matrix); Cleavage: Perfect rhombohedral in calcite matrix; Specific gravity: 2.71

Formation & geological history

Formed in warm, shallow marine environments from the accumulation of calcium carbonate and the skeletal remains of marine organisms. This specimen likely dates from the Paleozoic era (approx. 250-500 million years ago).

Uses & applications

Primarily used for educational collecting, decorative stone, and as a raw material for cement or lime production in industrial contexts.

Geological facts

Crinoids are also known as 'Sea Lilies' and are ancestors to modern starfish and sea urchins. The screw-like impression is a mold of a segmented stem.

Field identification & locations

Identify by looking for stacked, disc-like segments (chevrons) or circular impressions in a fine-grained gray rock. It will react and fizz when exposed to weak acid (vinegar). Found globally in ancient limestone beds.