Breciated Chert

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.

Identified on: 5/4/2026

Mode: Standard