sedimentary
Chert (Tan/Yellow variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, cream, or light yellow; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, cream, or light yellow
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, cream, or light yellow; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen appears water-worn, likely from a fluvial or coastal environment.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to sharp edges; currently used for road construction aggregate and sometimes as decorative stones in landscaping.
Geological facts
Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, which led to its historical use as flint in firearms and fire-starting tools.
Field identification & locations
Identify in the field by its waxy texture and characteristic curved (conchoidal) breaks. Often found as nodules within limestone or as rounded pebbles in riverbeds.
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