sedimentary
Chert / Flint
Cryptocrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture with sharp edges, various colors including gray, brown, white, and yellowish.
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Physical properties
Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture with sharp edges, various colors including gray, brown, white, and yellowish.
Formation & geological history
Formed in marine environments through the replacement of calcium carbonate by silica in limestone or chalk, or by the accumulation of siliceous oozes from microscopic organisms over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire; currently used in aggregate, abrasive industries, and decorative landscaping.
Geological facts
Ancient humans prized chert and flint for their ability to fracture conchoidally, producing extremely sharp edges ideal for cutting tools and weapons.
Field identification & locations
Can be identified in the field by its hardness (scratches glass), waxy luster, and distinctive conchoidal fracture. Often found as nodules within limestone or chalk formations worldwide.
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