sedimentary
Chert (variations include Flint/Jasper)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, or lavender-brown (as pictured), Luster: waxy to dull, Crystal Structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, or lavender-brown (as pictured), Luster: waxy to dull, Crystal Structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or by the precipitation of silica from groundwater within sedimentary layers like limestone or chalk.
Uses & applications
Historically used for stone tools and arrowheads; currently used as a road aggregate, in jewelry (as Jasper/Agate), and for making fire with steel.
Geological facts
Because of its conchoidal fracture, it breaks into sharp edges, making it the primary material for prehistoric survival tools globally. It is extremely durable and weather-resistant.
Field identification & locations
Identify by its waxy texture and sharp, shell-like (conchoidal) breaks. It will easily scratch glass. Commonly found in riverbeds, limestone outcrops, and coastal areas.
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