sedimentary

Flint (chert), likely brown flint

Microcrystalline quartz/chalcedony (SiO₂)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown to reddish-brown, waxy to dull luster, opaque to slightly translucent edges, and no visible crystal faces or cleavage. The sharp, curved edges and conchoidal fractures are characteristic of flint.

Identified August 10, 2026More sedimentary →

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Physical properties

Formation & geological history

A dense variety of chert formed when silica replaces or fills pores in marine or freshwater sediment, commonly from biogenic silica or silica-rich groundwater. The specimen’s exact geological age cannot be determined from the photograph; flint is widespread in Mesozoic and Cenozoic sediments.

Uses & applications

Used historically for stone tools and fire-starting, and occasionally as decorative rough material or lapidary pieces. It has little commercial value unless unusually colored or worked.

Geological facts

Flint fractures into extremely sharp edges and was crucial to prehistoric toolmaking. Brown coloration commonly results from iron oxides or included organic material.

Field identification & locations

Likely regional: flint and other cherts are common in the sedimentary rocks and gravels around central Hungary near 47.6°N, 19.3°E. Confirm with a scratch test against glass (it should scratch glass), a conchoidal fracture, and absence of fizzing in dilute acid.