sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: tan, grey, or creamy-white; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none, exhibits conchoidal fracture.
- Hardness
- 7 (Mohs scale)
- Color
- tan, grey, or creamy-white
- Luster
- waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: tan, grey, or creamy-white; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none, exhibits conchoidal fracture.
Formation & geological history
Formed in sedimentary environments from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or precipitation from groundwater within limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires; currently used as construction aggregate, road surfacing, and as a collector's specimen.
Geological facts
Chert is so hard it can scratch steel. When it breaks, it forms razor-sharp edges, which is why it was the primary material for arrowheads and scrapers for thousands of years.
Field identification & locations
Identify by its waxy texture and shell-like (conchoidal) fractures. Often found as rounded pebbles on beaches or nodules in limestone outcrops.
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