sedimentary

Chert Arrowhead

Microcrystalline Quartz (SiO2)

Hardness of 7 on the Mohs scale, grey and speckled color with weathered brown spots, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.60 to 2.65.

Identified August 1, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, grey and speckled color with weathered brown spots, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.60 to 2.65.

Formation & geological history

Formed in sedimentary environments through the replacement of limestone or chalk by silica-rich groundwater, or accumulation of siliceous skeletal remains of marine organisms over millions of years.

Uses & applications

Historically used by indigenous peoples for making sharp stone tools, projectile points, and cutting implements. Highly valued by artifact collectors and archaeologists.

Geological facts

Chert (often called flint when found in chalk) was one of the most prized materials for prehistoric stone tool technology due to its ability to fracture predictably and hold a very sharp edge.

Field identification & locations

Identified by its conchoidal fracture and waxy luster, often worked intentionally by human hands to create notches and sharp edges. Found globally in sedimentary rock formations.