sedimentary
Chert or Jasper
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: dull reddish-brown with grey/green weathering; Luster: waxy to dull; Structure: microcrystalline/cryptocrystalline; Fracture: conchoidal; SG: 2.6-2.7.
- Hardness
- 6
- Color
- dull reddish-brown with grey/green weathering
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: dull reddish-brown with grey/green weathering; Luster: waxy to dull; Structure: microcrystalline/cryptocrystalline; Fracture: conchoidal; SG: 2.6-2.7.
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. Often found in nodules or bedded deposits.
Uses & applications
Historically used for stone tools (arrowheads); currently used as aggregate, decorative stone, and in lapidary work for jewelry.
Geological facts
Chert is one of the most durable sedimentary rocks and was essential to early human civilizations for creating sharp-edged cutting tools and fire-starting flint.
Field identification & locations
Identify by its hardness (cannot be scratched by steel) and smooth, curved shell-like (conchoidal) fractures. Common in limestone outcrops and riverbeds.
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