sedimentary
Flint / Chert Pebble
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale; conchoidal fracture with sharp edges; waxy to vitreous luster; opaque to translucent; colors range from brown, grey, white, to black often showing patination from weathering.
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Physical properties
Hardness of 7 on the Mohs scale; conchoidal fracture with sharp edges; waxy to vitreous luster; opaque to translucent; colors range from brown, grey, white, to black often showing patination from weathering.
Formation & geological history
Formed diagenetically through the replacement of calcium carbonate in limestone or chalk by silica-rich solutions over millions of years.
Uses & applications
Historically used for stone tools, arrowheads, and fire-starting (striking against steel); currently used for decorative landscaping, road aggregates, and abrasive grinding pebbles.
Geological facts
Flint and chert are chemically identical forms of microcrystalline quartz, but 'flint' traditionally refers to nodules found in chalk formations. Its conchoidal fracture makes it exceptionally suitable for knapping.
Field identification & locations
Easily identified by its smooth, water-worn shape, waxy luster, and distinctive conchoidal fracture surfaces. Commonly found along beaches, riverbeds, and chalk or limestone cliffs worldwide.
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