sedimentary
Green Chert
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Pale green to olive green; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (shows conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Pale green to olive green
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Pale green to olive green; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (shows conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation in marine environments. Often found in nodules or bedded layers within limestone or shale.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its sharp fracture edges. Today it is used as a semi-precious gemstone, in landscaping, and as a material for lapidary work.
Geological facts
Chert is so hard it can strike sparks against steel, making it useful for early flintlock firearms. Specific green varieties are sometimes colloquially called 'greenstone' or incorrectly labeled as jade by amateurs.
Field identification & locations
Identify by its waxy texture, extreme hardness (it will scratch glass), and its characteristic shell-like (conchoidal) curved fracture lines when broken. Commonly found in river beds or erosion sites near sedimentary basins.
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