sedimentary
Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 Mohs scale. Color: Tan, beige, or yellowish-brown. Luster: Dull to waxy. Crystal Structure: Trigonal (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
- Hardness
- 7 Mohs scale
- Color
- Tan, beige, or yellowish-brown
- Luster
- Dull to waxy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs scale. Color: Tan, beige, or yellowish-brown. Luster: Dull to waxy. Crystal Structure: Trigonal (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or by the chemical replacement of limestone/dolomite by silica-rich fluids. Generally dates from various geological eras, frequently found in nodules within limestone beds.
Uses & applications
Historically used for stone tools/weapons (knapping) and fire-starting. Currently used in road construction, as a filler in cement, and sometimes as a minor gemstone when colorful (Jasper).
Geological facts
Chert breaks with a conchoidal fracture, creating sharp edges that made it the primary material for arrowheads and scrapers for prehistoric humans for thousands of years.
Field identification & locations
Identify by its hardness (scratches glass), waxy質感, and sharp, curved fracture lines. It is common in regions with large limestone or chalk deposits like the midwestern United States and southern England.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary