sedimentary
Flint
SiO2 (Microcrystalline Quartz / Chert)
Hardness of 7 on the Mohs scale, typically gray, black, or dark brown in color, waxy to vitreous luster, cryptocrystalline structure, exhibits conchoidal fracture with no true cleavage, and a specific gravity of around 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically gray, black, or dark brown in color, waxy to vitreous luster, cryptocrystalline structure, exhibits conchoidal fracture with no true cleavage, and a specific gravity of around 2.60 to 2.65.
Formation & geological history
Formed as nodules and masses in sedimentary rocks such as chalk and limestone through the replacement of calcium carbonate by silica-rich solutions or the accumulation of siliceous skeletal remains of marine organisms.
Uses & applications
Historically used for making stone tools, arrowheads, and blades due to its sharp conchoidal fracture. Also used historically with steel to create sparks for starting fires.
Geological facts
Flint is a variety of chert. Because of its durability and ability to hold a sharp edge, it was one of the most important materials for early human technology during the Stone Age.
Field identification & locations
Can be identified in the field by its dark color, waxy luster, and distinctive conchoidal fracture resulting in very sharp edges. Commonly found embedded in chalk or limestone deposits worldwide.
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