sedimentary
Flint
SiO2 (Microcrystalline Quartz / Chert)
Hardness of 7 on the Mohs scale, dark gray to black color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.6.
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Physical properties
Hardness of 7 on the Mohs scale, dark gray to black color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.6.
Formation & geological history
Formed through the chemical replacement of limestone or chalk by silica-rich solutions or the accumulation of siliceous skeletal remains of marine organisms in deep marine environments over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and fire-starting (flint and steel). Currently used in decorative aggregates, road construction, and abrasive grit.
Geological facts
Flint is a variety of chert. When struck against steel, it produces sparks, making it crucial for early human survival and firearm mechanisms (flintlock rifles).
Field identification & locations
Found commonly as nodules or layers within chalk and limestone formations. Easily identifiable by its smooth, dark, rounded exterior rind and sharp, glass-like conchoidal fractures when broken.
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