sedimentary
Chert Breccia
Brecciated Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, or white matrix with reddish-brown clasts; Luster: Waxy to dull/earthy; Texture: Clastic (angular fragments in a finer matrix); Cleavage: None (conchoidal fracture)
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, or white matrix with reddish-brown clasts
- Luster
- Waxy to dull/earthy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, or white matrix with reddish-brown clasts; Luster: Waxy to dull/earthy; Texture: Clastic (angular fragments in a finer matrix); Cleavage: None (conchoidal fracture)
Formation & geological history
Formed through the mechanical breaking of chert beds followed by cementation with silica-rich fluids. Often associated with tectonic activity or karst collapse in Paleozoic to Mesozoic sedimentary basins.
Uses & applications
Used primarily as road base or aggregate in construction. High-quality specimens are occasionally used for landscaping or as lapidary rough for 'pudding stone' jewelry.
Geological facts
Breccia differs from conglomerate because its fragments are angular rather than rounded, indicating that the fragments did not travel far from their source before being cemented together.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and the presence of sharp, angular rock fragments cemented in a solid mass. Commonly found in areas with limestone or dolomite bedrock.
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