sedimentary
Chert (Arrowhead/Artifact Fragment)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 6.5–7 on Mohs scale. Color: White to light gray with possible blueish tints. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (exhibits conchoidal fracture which produces sharp, shell-like edges).
- Hardness
- 6
- Color
- White to light gray with possible blueish tints
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: White to light gray with possible blueish tints. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (exhibits conchoidal fracture which produces sharp, shell-like edges).
Formation & geological history
Formed through the precipitation of silica-rich fluids within sedimentary rock layers, often limestone or chalk. Many chert deposits formed during the Paleozoic or Mesozoic eras as silica-rich organic remains (like diatoms or radiolaria) recrystallized.
Uses & applications
Historically used for stone tools (lithics) like arrowheads and scrapers due to its sharpness. Modernly used in construction aggregate, road surfacing, and sometimes as a minor gemstone or for lapidary work.
Geological facts
This specific piece appears to be a man-made lithic flake or a fragment of a projectile point (arrowhead), indicated by the intentional pressure-flaking scars on its edges. Chert was the 'steel of the ancient world' because its fracture pattern allows for edges sharper than a surgical scalpel.
Field identification & locations
Identify in the field by its hardness (it will scratch glass and steel), waxy texture, and conchoidal fracture patterns. Found globally in sedimentary basins. Collectors should look for 'retouch' marks or flaking patterns that indicate human modification rather than natural weathering.
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