sedimentary

Dark shale or mudstone

Fine-grained sedimentary rock composed mainly of clay minerals and quartz; exact identification is uncertain from the image.

AI-generated identification · may be incorrect

Dark gray-brown, dull, very fine-grained, and apparently fissile or fractured into thin irregular pieces. Typical shale has Mohs hardness about 2–3; crystal structure is not visible.

Identified October 9, 2026More sedimentary →

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Physical properties

Dark gray-brown, dull, very fine-grained, and apparently fissile or fractured into thin irregular pieces. Typical shale has Mohs hardness about 2–3; crystal structure is not visible.

Formation & geological history

Forms as compacted clay- and silt-rich mud in quiet-water settings such as lakes, floodplains, or marine basins. Its age cannot be determined from the image.

Uses & applications

Shale is used in cement and brick manufacture and, in some settings, as a source rock for oil and gas; this fragment has no evident gem or display value.

Geological facts

Shale commonly splits along bedding planes, while mudstone is similar but less fissile; the photograph does not show enough detail to distinguish them confidently.

Field identification & locations

The dark, fine-grained, layered-looking fragments are consistent with shale or mudstone, but scale and fresh surfaces would help confirm it. These rocks occur widely in sedimentary basins worldwide.