sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: tan/brownish-gray, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan/brownish-gray, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary basins. Most specimens date from the Precambrian to the present.
Uses & applications
Historically used for stone tools and weapons (knapping); modernly used for road surfacing, grinding media, and as a starting material for silicon production.
Geological facts
Chert has a unique property where it breaks into very sharp edges, leading to its usage by early humans for tools. It is functionally identical to flint, though usually lighter in color.
Field identification & locations
Look for visible conchoidal fractures (shell-like curves) and a waxy texture. It is extremely hard and will scratch glass. Common in limestone or chalk deposits.
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