sedimentary
Chert (Jasper-like Silicate)
Silicon Dioxide (SiO2)
Hardness: 7 Mohs, Color: Tan to yellowish-brown (likely due to iron oxides), Luster: Waxy to dull, Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal/Hexagonal), Cleavage: None (Conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 Mohs, Color: Tan to yellowish-brown (likely due to iron oxides), Luster: Waxy to dull, Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal/Hexagonal), Cleavage: None (Conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids within sedimentary environments. This specific specimen shows signs of water-wear or smoothing over geological time within a fluvial (river) or glacial environment.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp conchoidal fracture. Modern uses include landscaping, gravel, and lapidary work (polishing) for jewelry.
Geological facts
Chert is extremely durable and chemically inert. Varieties of chert include flint, jasper, and agate. It was one of the most vital resources for prehistoric humans globally.
Field identification & locations
Identify in the field by its hardness (it will scratch glass and steel), its smooth waxy feel, and its curved, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds, limestone outcrops, and glacial tills.
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