sedimentary
Chert / Greenstone
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5-7 (Mohs); Color: Olive green to grayish-green; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 6
- Color
- Olive green to grayish-green
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Olive green to grayish-green; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in marine environments; may have undergone low-grade metamorphism (greenstone transition).
Uses & applications
Historically used for stone tools/arrowheads; currently used as decorative gravel, in lapidary work (polishing), and as a collection specimen.
Geological facts
This specimen shows the characteristic smooth, waxy surface and conchoidal fracturing common in cherts. The green hue often results from chlorite or iron inclusions.
Field identification & locations
Identify by its ability to scratch glass and smooth, 'plasticky' feel. Commonly found in riverbeds, glacial tills, and coastal areas throughout the Pacific Northwest and Appalachia.
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