sedimentary

Green Chert

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Olive to forest green; Luster: Waxy to vitreous; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Olive to forest green
Luster: Waxy to vitreous

Identified June 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains, such as radiolaria or diatoms, on the ocean floor, which later undergo diagenesis and compaction. Often found in marine sedimentary sequences.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges when broken. Today used in lapidary work, landscaping, and as a geological indicator.

Geological facts

Green chert often gets its color from chlorite or other mineral inclusions. In some regions, specific green cherts are referred to as 'greenstone' or 'jasper', though chert is the broader sedimentary term.

Field identification & locations

Identify in the field by its waxy luster, extreme hardness (scratches steel), and characteristic conchoidal (shell-like) fracture patterns. Frequently found in riverbeds or coastal cliffs in California and the Pacific Northwest.