sedimentary
Chert Breccia
Brecciated Chert (SiO2)
Hardness: 7 Mohs; Color: Tan, brown, and grey; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 Mohs
- Color
- Tan, brown, and grey
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 Mohs; Color: Tan, brown, and grey; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the mechanical breakage of chert layers due to tectonic activity or collapse, followed by the cementation of these angular fragments by silica-rich fluids (often during the Phanerozoic eon).
Uses & applications
Used primarily in construction aggregate, road base, and occasionally as a decorative landscape stone or for primitive tool making lapidary.
Geological facts
Unlike conglomerates which have rounded pebbles, breccias have sharp, angular fragments indicating the material did not travel far after breaking.
Field identification & locations
Identify in the field by its hardness (scratches glass), angular internal clasts, and waxy texture. Commonly found in limestone regions or near fault zones.
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