sedimentary
Chert (variations include Flint or Jasper)
Chert (Silicon Dioxide, SiO2)
Hardness: 6.5–7 on Mohs scale. Color: White, tan, or grey (in this specimen). Luster: Waxy to dull. Crystal Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.7.
- Hardness
- 6
- Color
- White, tan, or grey (in this specimen)
- Luster
- Waxy to dull
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5–7 on Mohs scale. Color: White, tan, or grey (in this specimen). Luster: Waxy to dull. Crystal Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.7.
Formation & geological history
Formed from the precipitation of silica-rich fluids or the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools (arrowheads/knives) due to its sharp edges. Today used in construction aggregate, road surfacing, and as a component in ceramics.
Geological facts
Because of its conchoidal fracture pattern, chert breaks with extremely sharp edges, which is why it was the primary material for the 'Stone Age.' It is physically and chemically very resistant to weathering.
Field identification & locations
Identify in the field by its waxy texture, smooth curved (conchoidal) breaks, and its ability to scratch glass. It will not fizz with acid, distinguishing it from limestone. Commonly found in riverbeds or as nodules protruding from limestone cliffs.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary