sedimentary
Chert (Flint/Novaculite)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: White to light gray; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- White to light gray
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: White to light gray; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms or through chemical precipitation in sedimentary environments. Common in Paleozoic and Mesozoic rock layers.
Uses & applications
Historical use for stone tools and weapons (flint knapping); currently used in road construction aggregate, as sharpening stones (novaculite), and in glass manufacturing.
Geological facts
Chert is so hard it can scratch steel and was one of the primary materials used by prehistoric humans to start fires and make arrowheads due to its sharp, glass-like fracture patterns.
Field identification & locations
Identify in the field by its smooth, waxy surface and conchoidal (curved/shell-like) fractures. Found globally in limestone formations and as nodules in stream beds.
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Cone-in-cone structure (Secondary Sedimentary Structure)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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Shale or Slaty Mudstone
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