sedimentary

Chert with Calcite Veining

Microcrystalline Quartz (SiO2) with Calcium Carbonate (CaCO3) veins

AI-generated identification · may be incorrect

Hardness: 7 (chert) / 3 (veins); Color: Black to dark grey matrix with white veins; Luster: Waxy to sub-vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)

Hardness: 7 (chert) / 3 (veins)
Color: Black to dark grey matrix with white veins
Luster: Waxy to sub-vitreous

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 7 (chert) / 3 (veins); Color: Black to dark grey matrix with white veins; Luster: Waxy to sub-vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)

Formation & geological history

Formed in marine sedimentary environments where silica-rich fluids replaced organic matter or limestone; the white veins formed later when tectonic stress cracked the rock and minerals (likely calcite or quartz) precipitated in the voids. Commonly found in the Zagros Mountains region of Iran.

Uses & applications

Historically used for stone tools due to sharp fracture edges; currently used for decorative garden stones, road aggregate, or as a specimen for geological study.

Geological facts

The region near Shiraz (the user's coordinates) part of the Zagros Fold-Thrust Belt, is famous for extensive sedimentary sequences where dark chert and limestone with secondary veining are extremely common.

Field identification & locations

Identify in the field by its hardness (chert will scratch steel) and its characteristic smooth, curved fracture surfaces. Calcite veins will fizz if touched with weak acid (vinegar).