sedimentary

Fossiliferous Flint / Chert

Microcrystalline quartz (SiO2) with embedded invertebrate fossils

Hardness of 7 on the Mohs scale, colors ranging from white, grey, brown to yellowish-tan due to iron staining, waxy to vitreous luster, cryptocrystalline or microcrystalline structure, conchoidal fracture, specific gravity of approximately 2.60 to 2.65.

Identified August 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine environments through the replacement of calcium carbonate in limestone by silica-rich solutions or the accumulation of siliceous skeletal remains of marine organisms, often dating back to the Cretaceous period.

Uses & applications

Historically used for stone tools and fire-starting; today primarily of interest to fossil and rock collectors, and occasionally used in landscaping or decorative masonry.

Geological facts

Flint and chert nodules frequently preserve ancient marine fossils such as brachiopods, bivalves, and crinoids, offering a window into prehistoric ocean life.

Field identification & locations

Can be identified in the field by its extreme hardness (scratches glass), conchoidal fracture pattern, waxy texture, and visible fossil impressions or fragments on the weathered surface.

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Sandstone or Siltstone

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