sedimentary
Chert / Flint
Microcrystalline or cryptocrystalline quartz (SiO2)
Hardness: 6.5-7. Color: varying shades of red, brown, yellow, and gray due to impurities. Luster: waxy to dull. Cleavage: none, exhibits conchoidal fracture.
- Hardness
- 6
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7. Color: varying shades of red, brown, yellow, and gray due to impurities. Luster: waxy to dull. Cleavage: none, exhibits conchoidal fracture.
Formation & geological history
Forms as chemical sedimentary rock, often as nodules in limestone or massive bedded deposits. The red/brown coloration typically comes from iron oxide impurities.
Uses & applications
Historically used for making stone tools and starting fires. Currently used in road surfacing or simply collected.
Geological facts
Because it breaks with a conchoidal fracture (producing sharp edges), it was one of the primary materials used by early humans for arrowheads and scrapers.
Field identification & locations
Identify by its hardness (scratches glass), waxy luster, and conchoidal fracture. Often found in riverbeds or limestone outcrops.
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