sedimentary
Chert Nodule
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to light brown; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan to light brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to light brown; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich fluids within sedimentary rock layers, primarily during the diagenesis of limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires; currently used in construction aggregate and as a collector's specimen.
Geological facts
Chert is so hard that it can scratch steel. When broken, it produces sharp, glass-like edges that made it the primary material for prehistoric arrowheads and scrapers.
Field identification & locations
Identified by its extreme hardness, smooth conchoidal fracture, and waxy surface when freshly broken. Commonly found in limestone outcrops or as river-worn pebbles.
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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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