sedimentary
Chert / Flint
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, colors range from gray, white, and brown to black, specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, colors range from gray, white, and brown to black, specific gravity of 2.60 to 2.65.
Formation & geological history
Formed via the chemical replacement of limestone or chalk by silica-rich solutions, or through the accumulation of siliceous skeletal remains of marine organisms such as diatoms and radiolarians over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire. Occasionally used for decorative carvings, jewelry, and industrial grinding.
Geological facts
Known as flint when found as nodules in chalk, and chert when found in limestone formations. It was one of the most critical materials for prehistoric human survival due to its ability to fracture with extremely sharp edges.
Field identification & locations
Can be identified by its distinctive conchoidal (shell-like) fracture, hardness that easily scratches glass, and waxy luster. Common globally in sedimentary rock layers worldwide.
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