sedimentary

Fossiliferous Sandstone Pebble (with Crinoid / Shell Impression)

Sandstone containing fossiliferous inclusions (SiO2 matrix with calcite/silica cast fossil)

AI-generated identification · may be incorrect

Hardness: 6-7 (quartz sand matrix); Color: Tan, brownish-gray, with light crystalline fossil cast markings; Luster: Dull, earthy matrix with vitreous fossil replacement; Texture: Fine to medium-grained, rounded water-worn pebble.

Hardness: 6-7 (quartz sand matrix)
Luster: Dull, earthy matrix with vitreous fossil replacement

Identified July 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in shallow marine environments where sand accumulated alongside organic remains (such as crinoids, corals, or mollusks). Over time, compaction and cementation formed sandstone, while water erosion rounded the stone into a beach/river cobble.

Uses & applications

Landscaping, aggregate, educational tool, and local geological collecting.

Geological facts

Rocks like this often preserve 'trace fossils' or hollow molds where organic shell matter dissolved away, leaving a cavity or crystalline replacement. Water-rounded fossiliferous pebbles are often referred to as 'hag stones' or 'adder stones' if the hole passes completely through.

Field identification & locations

Identify in the field by looking for rounded river or beach stones displaying distinct curved, patterned, or crystalline fossil cross-sections. Commonly found in riverbeds, glacial deposits, and coastal beaches worldwide.