sedimentary

Green Chert

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs); Color: Pale green to olive; Luster: Waxy to dull; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Pale green to olive
Luster: Waxy to dull

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Pale green to olive; Luster: Waxy to dull; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Formation & geological history

Formed from the accumulation of silica-rich organic remains, such as radiolaria or diatoms, on the ocean floor, followed by diagenesis into dense microcrystalline quartz.

Uses & applications

Historically used for stone tools/arrowheads; currently used in landscaping, as a gemstone in tumbled form, and as a source of silica.

Geological facts

Chert is so hard it can scratch steel. The green color in specimens like this is often caused by the inclusion of chlorite or other mineral impurities during formation.

Field identification & locations

Look for a smooth, waxy surface and characteristic shell-like (conchoidal) fractures. It is commonly found in sedimentary sequences like the Franciscan Complex in California.