sedimentary
Chert / Flint Pebble
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, colors typically range from white, grey, beige to brown or dark grey, waxy to dull luster, cryptocrystalline structure with conchoidal fracture.
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Physical properties
Hardness of 7 on the Mohs scale, colors typically range from white, grey, beige to brown or dark grey, waxy to dull luster, cryptocrystalline structure with conchoidal fracture.
Formation & geological history
Formed via the chemical replacement of limestone or chalk by silica-rich solutions or the accumulation of siliceous skeletal remains of marine organisms in deep ocean environments.
Uses & applications
Historically used for making stone tools, arrowheads, and friction-based fire starters; currently used in abrasives, road aggregate, and as a decorative stone.
Geological facts
Chert and flint are essentially the same material, though historically 'flint' is often used for darker varieties found in chalk formations while 'chert' refers to lighter varieties in limestone.
Field identification & locations
Easily identified in the field by its hard conchoidal (shell-like) fracture edges, waxy feel, and ability to scratch glass. Commonly found as nodules or pebbles in chalk and limestone riverbeds and beaches.
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