sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Tan, brown, and yellow hues (iron stained); Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Tan, brown, and yellow hues (iron stained)
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Tan, brown, and yellow hues (iron stained); Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
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 chalk beds. This specimen shows significant weathering from stream or glacial transport.
Uses & applications
Historically used for stone tools and reaching a spark (flint). Currently used as an abrasive, in road construction (crushed stone), and for decorative lapidary work.
Geological facts
Chert was one of the most vital materials for early humans because its conchoidal fracture allows it to be chipped into extremely sharp blades and arrowheads.
Field identification & locations
Identify by its hardness (it will scratch glass), waxy feel when smooth, and smooth, curved fracture surfaces. Commonly found in riverbeds, fields, and sedimentary outcrops worldwide.
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