sedimentary

Likely brown chert or flint fragment

Microcrystalline quartz (SiO₂), commonly with iron-oxide impurities

AI-generated identification · may be incorrect

Typically dark brown to gray-brown, waxy to dull luster, very fine-grained and lacking visible crystals; Mohs hardness about 7, conchoidal fracture, no cleavage, specific gravity about 2.6. The specimen appears naturally fractured or possibly shaped, but the blurry image prevents confident identification.

Identified August 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica precipitates or replaces sediments, often in limestone or chalk, during diagenesis; its age may range from Precambrian to modern geological formations. Iron oxides produce the brown coloration.

Uses & applications

Used historically for sharp tools and fire-starting, and occasionally as a lapidary or decorative material; ordinary pieces have little commercial value.

Geological facts

Fresh edges can be extremely sharp because of conchoidal fracture. Flint is a dark, compact variety of chert, often associated with chalk deposits.

Field identification & locations

Common in sedimentary terrains worldwide, especially limestone regions. Test for a glassy conchoidal fracture and inability to scratch it with a steel blade; quartz-rich chert can scratch glass, whereas glassy slag may look similar.