sedimentary
Flint
SiO2 (Microcrystalline Quartz / Chert)
Hardness of 7 on the Mohs scale. Color ranges from grey, bluish-grey, black, to dark brown. Exhibits a waxy to vitreous luster and typically breaks with a very sharp conchoidal fracture. Cryptocrystalline structure.
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Physical properties
Hardness of 7 on the Mohs scale. Color ranges from grey, bluish-grey, black, to dark brown. Exhibits a waxy to vitreous luster and typically breaks with a very sharp conchoidal fracture. Cryptocrystalline structure.
Formation & geological history
Formed as nodules or concretions in sedimentary rock, principally chalk or limestone, through the replacement of calcium carbonate by silica-rich solutions over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-producing fire starters. Modern uses include abrasives and industrial milling.
Geological facts
Flint is famous for its ability to produce sparks when struck against steel due to its hardness and microcrystalline structure. It has been utilized by humans for hundreds of thousands of years.
Field identification & locations
Easily identified by its distinctive conchoidal fracture, sharp edges, waxy luster, and occurrence as nodules within chalk or limestone formations.
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