sedimentary
Flint
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale; color ranges from grey, brown, to dark black with a white or grey outer cortex; waxy to vitreous luster; cryptocrystalline structure; conchoidal fracture with no cleavage; specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; color ranges from grey, brown, to dark black with a white or grey outer cortex; waxy to vitreous luster; cryptocrystalline structure; conchoidal fracture with no cleavage; specific gravity of 2.60 to 2.65.
Formation & geological history
Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions during the Cretaceous period, typically millions of years ago.
Uses & applications
Historically used for making stone tools, weapons, and fire-starting flintlocks; today used primarily in decorative landscaping, road construction, and historical reenactments.
Geological facts
Flint has been utilized by early humans for over two million years due to its ability to fracture into extremely sharp edges. It is a variety of chert specifically found in chalk or marly limestone formations.
Field identification & locations
Easily identified in the field by its conchoidal fracture, sharp edges, waxy luster, and frequent white chalky outer cortex. Common on beaches and chalk downlands, particularly in regions like Southern England, France, and parts of North America.
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