sedimentary
Breciated Chert
Brecciated Chert (Microcrystalline Quartz, SiO2)
Hardness: 7 Mohs; Color: Brown, tan, and white; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Brown, tan, and white
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 Mohs; Color: Brown, tan, and white; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the mechanical fracturing of silica-rich sedimentary rock (chert) followed by the cementation of the fragments with fine-grained minerals or secondary quartz during diagenesis.
Uses & applications
Primarily used for decorative purposes, river rock landscaping, lapidary work (cabochons), and as educational specimens due to its distinct angular internal structure.
Geological facts
The term breccia comes from the Italian word for rubble. In chert, this often indicates significant tectonic movement or hydrothermal activity that shattered the original rock bed.
Field identification & locations
Identify in the field by its hardness (scratches glass), waxy texture when wet, and the visible angular segments (clasts) held together by a matrix. Commonly found in riverbeds or areas with limestone/dolomite deposits.
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