sedimentary
Chert (often called Flint in this context)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brown, gray, and cream with possible mottling; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (displays conchoidal fracture); Specific Gravity: 2.5-2.8
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, gray, and cream with possible mottling
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, gray, and cream with possible mottling; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (displays conchoidal fracture); Specific Gravity: 2.5-2.8
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or the chemical replacement of limestone by silica-rich fluids. This specimen shows weathering typical of surface-found material.
Uses & applications
Historically used for stone tools (lithic reduction) such as arrowheads or scrapers. Today used as road aggregate, in fire-starting kits (flint and steel), and as a lapidary material for hobbyists.
Geological facts
Chert was one of the most important minerals to prehistoric humans because its conchoidal fracture produces extremely sharp edges. This specific piece has a triangular shape that resembles a rough or broken stone tool preform.
Field identification & locations
Identify in the field by its hardness (will scratch glass and steel), waxy texture when freshly broken, and the presence of curved, shell-like (conchoidal) fracture marks. Can be found in nodules within limestone or as worn pebbles in riverbeds.
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