sedimentary
Chert (Arrowhead/Projectile Point)
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Tan, white, and grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque.
- Hardness
- 6
- Color
- Tan, white, and grey
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Arrowhead/Projectile Point) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Tan, white, and grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Opaque.
Formation & geological history
Formed as nodules or beds in limestone or chalk through the accumulation of siliceous organisms or silica precipitation. This specimen has been anthropogenically modified by flintknapping, likely during the Archaic or Woodland period.
Uses & applications
Historically used for tools and weapons (arrowheads, scrapers, knives) due to its sharp edges; currently valued by archaeologists and lithic collectors.
Geological facts
Chert is one of the most common materials used by early humans for stone tools. The intentional shaping visible here is called 'pressure flaking', which creates the serrated edges and point.
Field identification & locations
Identify in the field by looking for conchoidal (shell-like) fracture scars and symmetrical shaping. Commonly found in creek beds or plowed fields near ancient water sources or flint outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary