sedimentary
Chert (specifically Jasper or Flint)
Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Brown, tan, and yellow-orange tones, Luster: Waxy to dull, Crystal structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Brown, tan, and yellow-orange tones, Luster: Waxy to dull, Crystal structure: Trigonal (microscopic), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms) or chemical precipitation from groundwater within sedimentary beds. This specimen likely formed in ancient marine environments or as nodules in limestone.
Uses & applications
Historically used for stone tools and weapons due to sharp edges; modernly used as road aggregate, in jewelry (lapidary), and as fire-starting flint.
Geological facts
Chert has a conchoidal fracture, meaning it breaks like glass. This property made it the most important material for early humans to create arrowheads and knives.
Field identification & locations
Identify by its waxy texture, extreme hardness (it will scratch glass), and curved, shell-like fracture marks. Commonly found in riverbeds or eroding out of limestone/dolomite cliffs.
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