sedimentary
Chert (Nodule)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: Variegated grey, tan, and brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Variegated grey, tan, and brown
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Nodule) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Variegated grey, tan, and brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; 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 replacement of limestone/chalk by silica in groundwater. Occurs throughout geological history from Precambrian to modern strata.
Uses & applications
Historically used for making stone tools (arrowheads). Modernly used in road construction, as an abrasive, and sometimes in landscaping or lapidary work.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture creates edges sharper than a steel scalpel. Varieties of chert include flint and jasper.
Field identification & locations
Identify in the field by its hardness (will scratch glass and steel), waxy appearance on fresh surfaces, and the way it breaks into curved, shell-like flakes. Commonly found in limestone beds.
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary