sedimentary
Chert (Jasper/Quartzite river stone)
Microcrystalline Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, tan, and reddish hues; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brown, tan, and reddish hues
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, and reddish hues; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. This specific specimen has been significantly smoothed and rounded by long-term fluvial (river) erosion.
Uses & applications
Commonly used for landscaping, decorative gravel, and historically as a material for knapping stone tools (arrowheads). Highly polished versions are used in jewelry as lapidary 'river stones'.
Geological facts
River-worn chert and jasper are among the most durable rocks found in nature. Because of their hardness and high silica content, they were the primary resource for Stone Age tools across nearly all continents.
Field identification & locations
Identify in the field by its smooth, egg-like shape, lack of visible grains, and ability to scratch glass. It will feel much heavier and denser than a similarly sized piece of limestone or sandstone.
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