sedimentary
Chert (Nodule)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Tan, brown, grey, yellowish; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic), trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 6
- Color
- Tan, brown, grey, yellowish
- 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 Mohs; Color: Tan, brown, grey, yellowish; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic), trigonal; 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 chemical precipitation from groundwater within sedimentary host rocks like limestone or chalk. Commonly found in Mesozoic or Paleozoic strata.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to conchoidal fracture which creates sharp edges. Currently used in construction aggregate and as decorative landscaping stones.
Geological facts
Chert was one of the most important raw materials for early humans; it is chemically identical to flint, but 'flint' is a term usually reserved for chert found specifically in chalk deposits.
Field identification & locations
Identify by its waxy appearance, extreme hardness (can scratch glass/steel), and smooth, curved shell-like fracture surfaces. Often found as rounded nodules in streambeds or weathered out of limestone cliffs.
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