sedimentary
Chert (Flint/Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Brownish-red to waxy tan with translucency, Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Brownish-red to waxy tan with translucency, Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed primarily by the accumulation of siliceous remains of marine organisms or by chemical precipitation in saltwater environments. It can occur as nodules or beds in limestone and chalk. Specimens of this age can range from hundreds of millions to billions of years old.
Uses & applications
Historically used for stone tools due to its sharp edges when fractured. Modern uses include jewelry (as jasper or agate), construction aggregate, and as a component in glass manufacturing.
Geological facts
The conchoidal fracture pattern (curved, shell-like breaks) allows it to produce some of the sharpest edges known to man, leading to its extensive use by early humans for arrowheads and scrapers.
Field identification & locations
Identify in the field by its smooth, waxy surface and its ability to scratch glass. It will often produce sparks when struck against steel. Commonly found in riverbeds or eroded from sedimentary rock layers.
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