sedimentary
Chert or Jasper
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: dull green to brown, Luster: waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal
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Physical properties
Hardness: 7 (Mohs scale), Color: dull green to brown, Luster: waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal
Formation & geological history
Formed by the precipitation of silica from seawater or the accumulation of silica-rich microfossils. Often found in nodules within limestone or as bedded deposits.
Uses & applications
Used historically for stone tools and arrowheads; currently used in jewelry (lapidary), as a gemstone, and in construction aggregate.
Geological facts
The smooth, waxy surface and sharp edges once broken made this a primary material for prehistoric humans to create cutting tools.
Field identification & locations
Field identification involves checking for a waxy luster and conchoidal (shell-like) fracture. It will easily scratch glass and cannot be scratched by a steel knife.
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