sedimentary
Chert (Jasper/Chalcedony mix)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Tan, brown, white, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6
- Hardness
- 6
- Color
- Tan, brown, white, and grey
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Tan, brown, white, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Often found as nodules in limestone or replaced organic matter. This specimen shows significant weathering on the outer rind.
Uses & applications
Historical use for stone tools and arrowheads; modern use in lapidary work, landscaping, and as a decorative mineral specimen.
Geological facts
Chert was one of the first materials used by early humans to create sharp tools due to its conchoidal fracture which produces razor-sharp edges. It is often synonymous with flint.
Field identification & locations
Identify in the field by its hardness (it can scratch glass and steel) and its smooth, shell-like fracture pattern. Commonly found in riverbeds and ancient sedimentary basins.
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