sedimentary

Flint or chert, possibly a knapped stone tool

Microcrystalline quartz (SiO₂), commonly chalcedony with possible carbonaceous impurities

AI-generated identification · may be incorrect

Typically dark gray to black, opaque, with a waxy-to-dull luster and very fine cryptocrystalline structure; Mohs hardness 6.5–7, no cleavage, conchoidal fracture, and specific gravity about 2.6. The pointed, irregular edges may indicate intentional knapping, though the image is too blurred for certainty.

Identified August 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or fills cavities in limestone and other sedimentary rocks, commonly during the Paleozoic–Mesozoic eras. Knapped pieces are human-processed geological specimens rather than naturally shaped rock.

Uses & applications

Used historically for cutting tools and fire-starting; modern uses include aggregate, decorative stone, and lapidary objects. Archaeological or well-made artifact specimens may be collectible.

Geological facts

Freshly fractured flint produces razor-sharp edges and may spark against steel. Color can result from organic matter, iron, or manganese impurities.

Field identification & locations

Identify by testing for glassy conchoidal fracture, inability to scratch it with a steel knife, and lack of visible grains or cleavage; avoid destructive tests on possible artifacts. Common in chalk and limestone regions worldwide.