sedimentary
Chert with Jasper/Quartz Inclusions
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Multi-colored with white, green, and reddish-brown bands; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Multi-colored with white, green, and reddish-brown bands
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Multi-colored with white, green, and reddish-brown bands; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed primarily as a chemical precipitate or through the accumulation of siliceous remains of organisms in marine environments. The colors result from mineral impurities like iron (red) or chlorite (green) during the replacement process.
Uses & applications
Commonly used for lapidary work such as tumbling and cabochon making. Historically used by ancient cultures for tool making (arrowheads/scrapers) due to its sharp fracture edges.
Geological facts
This specimen appears to be a 'river rock' or tumbled piece where different phases of silica (jasper, agate, and chert) have intertwined. Chert is often tough enough to survive long-distance transport in river beds.
Field identification & locations
Identify in the field by its hardness (will scratch glass), smooth waxy texture when wet, and characteristic conchoidal fracture. Often found in gravel pits or riverbeds near sedimentary basins.
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