sedimentary
Chert
Chert (Microcrystalline Quartz, SiO2)
Hardness: 6.5-7 on Mohs scale; Color: typically grey, tan, or brown with a dull to waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 6
- Color
- typically grey, tan, or brown with a dull to waxy luster
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: typically grey, tan, or brown with a dull to waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed by the accumulation of microcrystalline silica, often from the remains of silica-secreting organisms like diatoms or radiolarians, or through chemical precipitation in marine or groundwater environments.
Uses & applications
Historically used for stone tools and arrowheads due to its sharp edges; and today used for road aggregate and decoratively in landscaping.
Geological facts
Chert has been used by humans for millions of years to create tools. Flint is a variety of chert. It can often contain micro-fossils only visible under a microscope.
Field identification & locations
Check for conchoidal (shell-like) fracturing and high hardness (it will scratch glass). Often found as nodules within limestone or as bedded layers in sedimentary sequences.
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