sedimentary
Chert / Fossiliferous Limestone
Sedimentary Chert (often containing CaCO3 or SiO2 replacements)
Hardness: 6.5 to 7 on Mohs scale; Color: Tan, beige, grey; Luster: Waxy to dull; Crystal structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Tan, beige, grey
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5 to 7 on Mohs scale; Color: Tan, beige, grey; Luster: Waxy to dull; Crystal structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the precipitation of silica from sea water or by the replacement of calcium carbonate in limestone by silica during diagenesis. Commonly found in Paleozoic to Mesozoic sedimentary layers.
Uses & applications
Historical use for stone tools and arrowheads; currently used as aggregate, decorative stone, and studied for paleontological evidence.
Geological facts
This specimen shows internal fossiliferous structures, likely remnants of marine organisms like crinoids or shell fragments that have been replaced by silica.
Field identification & locations
Identify by its waxy luster, conchoidal fracture (curved surfaces), and the fact that it can scratch glass. Common in river beds and limestone outcrops globally.
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