sedimentary
Chert / Jasper
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and creamy white patches. Luster: Dull to waxy. Structure: Microcrystalline or cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Tan, brown, and creamy white patches
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and creamy white patches. Luster: Dull to waxy. Structure: Microcrystalline or cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed as a chemical precipitate or through the replacement of limestone by silica-rich fluids. Often found in nodules or bedded deposits within sedimentary layers.
Uses & applications
Historically used for stone tools and arrowheads due to its sharp edges; currently used for road surfacing, landscaping, and lapidary work.
Geological facts
Chert was one of the first materials used by early humans to create sparks and sharp tools. It is extremely resistant to chemical weathering.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its smooth, shell-like (conchoidal) fracture surfaces when broken. Common in creek beds and limestone outcrops.
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Brecciated Chert (Microcrystalline Silica)
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