sedimentary
Banded Chert (River Stone)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, and cream banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque to translucent.
- Hardness
- 6
- Color
- Brown, tan, and cream banding
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, and cream banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque to translucent.
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or freshwater environments. This specific specimen has been smoothed and rounded by water transport in a river or beach setting.
Uses & applications
Commonly used for lapidary work, decorative landscaping, and historically for stone tools due to its sharp edges when broken.
Geological facts
Chert is extremely durable and chemically stable. Varieties with specific colors or banding patterns are often called jasper. It was one of the primary materials used by prehistoric humans for creating arrowheads and scrapers.
Field identification & locations
Identify by its hardness (it can scratch glass), smooth waxy texture, and the presence of distinct bands or layers. Found worldwide in riverbeds and sedimentary outcrops.
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