sedimentary
Chert (Tan/Buff Chert)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, buff, or cream; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic atoms); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, buff, or cream
- Luster
- Waxy to dull
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Tan, buff, or cream; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic atoms); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation from silica-rich fluids in marine or groundwater environments. It typically forms as nodules or bedded layers within limestone or chalk.
Uses & applications
Historically used for making stone tools (arrowheads/scrapers) due to its sharp edges. Modernly used as road aggregate, in glass manufacturing, or as decorative landscaping stone.
Geological facts
Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, leading to its historical use as 'flint' in firearms and fire-starting kits.
Field identification & locations
Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its inability to be scratched by a steel knife. It often feels denser and smoother than surrounding limestone.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary