sedimentary
Green Chert
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: dull green to olive; Luster: waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: none, exhibits conchoidal fracture; Specific gravity: approx 2.65.
- Hardness
- 6
- Color
- dull green to olive
- Luster
- waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: dull green to olive; Luster: waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: none, exhibits conchoidal fracture; Specific gravity: approx 2.65.
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments; typically Paleozoic to Mesozoic in age.
Uses & applications
Historically used for stone tools (arrowheads/scrapers), currently used as decorative gravel, in lapidary work, and as a geological study specimen.
Geological facts
Green chert is often associated with the Franciscan Complex in California; it is a tough, durable rock that was highly prized by indigenous peoples for its sharp edge when flaked.
Field identification & locations
Identify in the field by its hardness (will scratch glass), waxy appearance, and characteristic shell-like (conchoidal) curved breaks. Common in coastal mountain ranges.
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