sedimentary
Chert (Brown Variety)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, tan, waxy luster; Crystal Structure: Hexagonal (microscopic); Fracture: Conchoidal (shell-like); Opaque to translucent edges.
- Hardness
- 6
- Color
- Brown, tan, waxy luster
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, waxy luster; Crystal Structure: Hexagonal (microscopic); Fracture: Conchoidal (shell-like); Opaque to translucent edges.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation from silica-saturated fluids in limestone or chalk beds.
Uses & applications
Historically used for stone tools and arrowheads; used today in construction aggregate, as a gemstone (Jasper/Flint variants), and for fire-starting.
Geological facts
Chert is extremely durable and chemically stable. Flaked chert specimens are among the oldest artifacts found in human history, dating back millions of years.
Field identification & locations
Identify by its 'waxy' appearance and sharp, curved edges when broken. It will scratch glass and cannot be scratched by a steel knife. Commonly found in nodules within sedimentary rock layers.
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Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
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Shale or Slaty Mudstone
Argillaceous sedimentary rock
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Sandstone
Arenite (primarily SiO2)
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