sedimentary

Chert (with Epidote/Quartz veining)

Cryptocrystalline silica (SiO2) with Epidote/Quartz inclusions

Hardness: 6.5-7 (Mohs scale), Color: Reddish-brown with green/white veining, Luster: Waxy to dull, Crystal structure: Microcrystalline/Amorphous, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Hardness: 6

Identified June 28, 2026More sedimentary →

Explore Chert (with Epidote/Quartz veining) in the encyclopedia →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria) on the ocean floor, which were subsequently compressed, lithified, and subjected to hydrothermal flushing that created the mineral veins.

Uses & applications

Historically used for stone tools and fire-starting; currently used for decorative purposes, landscape gravel, and as a collector's specimen.

Geological facts

This specimen likely comes from a mélange (like the Franciscan Complex in California), where different rock types are mixed together by tectonic activity. The green veins are likely epidote or chlorite, indicating low-grade metamorphism.

Field identification & locations

Identify in the field by its hardness (will scratch glass), smooth waxy texture, and unique color patterns. Found commonly in coastal or mountain regions with former tectonic subduction zones.

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