sedimentary

Fossiliferous shale or mudstone

Siliciclastic shale/mudstone, chiefly clay minerals and quartz with fossil fragments

AI-generated identification · may be incorrect

Gray, very fine-grained, dull to weakly earthy luster, thinly bedded or fissile, and typically Mohs 2–3. The visible shell-like impressions or fragments indicate fossil content; cleavage is along bedding rather than crystal faces.

Identified August 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when clay- and silt-sized sediment accumulated in quiet marine or lake environments, compacted, and lithified; fossils were buried during deposition. Its precise geological age cannot be determined from the image alone.

Uses & applications

Used locally for fill, low-grade aggregate, and sometimes cement raw material; fossil-bearing specimens are mainly collected for education and display rather than jewelry.

Geological facts

Shale splits into thin layers, whereas mudstone is more massive; this specimen appears transitional. Fossils can include brachiopods, bivalves, or other shelly organisms, but exact identification requires close examination.

Field identification & locations

Look for fine layering, a powdery texture, low hardness, and fossils; it generally will not fizz strongly with dilute hydrochloric acid unless carbonate-rich. Common in sedimentary basins worldwide.