sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
Hardness: 7 Mohs; Color: Tan, yellowish-brown, cream; Luster: Dull to waxy; Structure: Clastic with angular fragments; Cleavage: None (conchoidal fracture on fresh surfaces)
- Hardness
- 7 Mohs
- Color
- Tan, yellowish-brown, cream
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 Mohs; Color: Tan, yellowish-brown, cream; Luster: Dull to waxy; Structure: Clastic with angular fragments; Cleavage: None (conchoidal fracture on fresh surfaces)
Formation & geological history
Formed through the mechanical fracturing of chert beds due to tectonic activity or collapse, followed by cementation by silica-rich groundwater. Often found in Phanerozoic sedimentary sequences.
Uses & applications
Mainly used as aggregate in construction or as a decorative specimen for collectors interested in sedimentary textures.
Geological facts
Chert is composed of microcrystalline or cryptocrystalline quartz. When it breaks into sharp fragments and is glued back together by nature, it forms this 'brecciated' texture.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and the visible angular fragments. Common in limestone regions and riverbeds where erosion brings it to the surface.
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