sedimentary
Chert (Arrowhead Fragment)
Chert / Microcrystalline Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, tan, white, and brown with waxy luster; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, white, and brown with waxy luster
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, tan, white, and brown with waxy luster; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of siliceous remains of organisms (radiolaria/diatoms) on the ocean floor or through the replacement of limestone by silica-rich fluids. Likely millions of years old, often found in Paleozoic or Mesozoic strata.
Uses & applications
Historically used for making stone tools and projectile points due to its conchoidal fracture. In modern times, used as a road construction aggregate, silicon source, or for archaeological study.
Geological facts
This specimen appears to be a worked stone or lithic flake, possibly an arrowhead fragment. Chert is essentially the same as flint, though 'flint' is often used to refer specifically to chert found in chalk deposits.
Field identification & locations
Identify in the field by its waxy texture and sharp, shell-like (conchoidal) fractures. Common in limestone deserts and riverbeds. Look for 'bulb of percussion' or 'scars' indicating human modification.
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