sedimentary
Flint
Silicon dioxide (Microcrystalline Quartz / Chert)
Hardness: 7 on the Mohs scale, Color: Brown, tan, gray, or black, Luster: Waxy to vitreous, Crystal structure: Microcrystalline/cryptocrystalline quartz (chalcedony), Cleavage: None (exhibits conchoidal fracture), Specific gravity: 2.60 - 2.65
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Physical properties
Hardness: 7 on the Mohs scale, Color: Brown, tan, gray, or black, Luster: Waxy to vitreous, Crystal structure: Microcrystalline/cryptocrystalline quartz (chalcedony), Cleavage: None (exhibits conchoidal fracture), Specific gravity: 2.60 - 2.65
Formation & geological history
Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions in marine environments during the Cretaceous period.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire. Modern uses include decorative items, landscaping, and abrasive applications.
Geological facts
Flint is a variety of chert. When struck against steel, it produces sparks, which made it essential for early firearms and fire-starting kits.
Field identification & locations
Identified by its distinctive conchoidal fracture, waxy luster, and ability to scratch glass easily. Commonly found in chalk formations and limestone cliffs globally.
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