sedimentary
Chert
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Cream/White (tan variations), Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Cream/White (tan variations), Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed thru the accumulation of remains of silica-rich organisms or chemical precipitation within sedimentary rock layers like limestone. Typically dating from various geological eras, including the Paleozoic.
Uses & applications
Historically used for stone tools and arrowheads; currently used in construction aggregate and as a collector's specimen.
Geological facts
Chert is extremely durable and weather-resistant. Many ancient civilizations used it to strike sparks for fire due to its hardness and silica content.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and smooth, shell-like fracture surfaces. Often found in riverbeds or as nodules inside limestone cliffs.
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