sedimentary
Chert (Jasper/Flint variant)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs, Color: Brown/Ochre with possible mineralization, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 Mohs, Color: Brown/Ochre with possible mineralization, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6-2.7
Formation & geological history
Formed by the accumulation of siliceous remains of organisms (radiolaria/diatoms) or by chemical precipitation in saltwater environments. It commonly forms nodules in limestone or chalk beds.
Uses & applications
Historically used for making stone tools and starting fires (flint). Currently used as a decorative stone, in jewelry (as Jasper), and as road aggregate.
Geological facts
Because it fractures with sharp edges, it was primary material for prehistoric arrowheads and scrapers. Its waxy texture helps distinguish it from other sedimentary rocks.
Field identification & locations
Identify in the field by its hardness (will scratch glass), sharp conchoidal fracture edges, and smooth, waxy surface. Often found in riverbeds or within limestone outcrops.
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