sedimentary

Chert or fine-grained slate-like stone

Microcrystalline quartz (SiO₂), possibly siliceous shale or slate

AI-generated identification · may be incorrect

Dark gray, dull to slightly waxy luster, very fine-grained and apparently naturally fractured or knapped; quartz-rich chert has Mohs hardness about 7, while slate is about 3–4 and splits along cleavage. Specific gravity is approximately 2.6–2.7.

Identified August 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich sediment or biological silica lithifies, commonly during the Paleozoic–Cenozoic; slate forms when shale undergoes low-grade metamorphism. The image alone cannot securely distinguish these materials.

Uses & applications

Chert is used for prehistoric tools, sharp edges, abrasives, and decorative stone; slate is used for roofing, tiles, and writing surfaces. This small fragment has mainly educational or minor collecting value.

Geological facts

The sharp, angular edge and dark uniform texture are compatible with a flaked chert artifact, but no diagnostic workmanship is certain from one image.

Field identification & locations

Look for conchoidal fracture and glassy edges for chert, versus planar foliation and easy splitting for slate. Common sources include sedimentary basins worldwide; avoid destructive testing if it may be archaeological.