sedimentary
Chert / Flint Nodular Fragment
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale; color varies from light grey, white, to dark grey and brown; vitreous to dull luster; cryptocrystalline structure; conchoidal fracture with very sharp edges; specific gravity around 2.60.
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Physical properties
Hardness of 7 on the Mohs scale; color varies from light grey, white, to dark grey and brown; vitreous to dull luster; cryptocrystalline structure; conchoidal fracture with very sharp edges; specific gravity around 2.60.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions or the replacement of limestone/chalk by silica-rich fluids during diagenesis in marine environments, often millions of years old spanning various geological periods.
Uses & applications
Historically used extensively by prehistoric humans for making stone tools, arrowheads, and blades due to its conchoidal fracture. Today used in crushed form for road construction and occasionally in decorative landscaping.
Geological facts
Chert and flint are essentially the same material; the term 'flint' is typically reserved for darker varieties found specifically in chalk deposits, while 'chert' is used more broadly for varieties found in limestone.
Field identification & locations
Easily identified by its extremely smooth conchoidal fracture, sharp edges when broken, hardness that easily scratches glass, and waxy to dull luster. Found worldwide in sedimentary rock formations, particularly limestones and chalks.
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