mineral

Possible flint or slag fragment

Microcrystalline quartz (chalcedony), or iron-rich industrial slag

AI-generated identification · may be incorrect

Small, opaque black-gray fragment with dull to slightly glassy luster and irregular fracture; possible flint would have Mohs hardness about 7, while slag varies widely. Crystal structure cannot be confirmed from the image.

Identified August 9, 2026More mineral →

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Physical properties

Formation & geological history

If flint, it formed as silica replacement in sedimentary limestone or chalk, commonly during the Cretaceous; if slag, it is a human-produced smelting byproduct rather than a natural rock.

Uses & applications

Flint is used historically for tools and fire-starting and is collected as a lithic material; slag has limited value except for industrial archaeology or specimen collecting.

Geological facts

The jagged dark shape and apparent glassy surface are compatible with either a flint chip or black metallurgical slag. A streak, hardness, and close inspection of bubbles would help distinguish them.

Field identification & locations

Test whether it scratches glass and leaves a white streak; visible rounded bubbles, metallic beads, or very low density favor slag, while a sharp conchoidal fracture and uniform texture favor flint. Common flint occurs in chalk and limestone regions worldwide.