sedimentary
Chert
Chert (Microcrystalline Quartz, SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: tan, cream, or light grey, Luster: waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Identified More sedimentary →
Explore Chert in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: tan, cream, or light grey, Luster: waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed by the precipitation of silica from groundwater or the accumulation of silica-rich microfossils (like radiolarians or diatoms) in marine environments. Often found as nodules in limestone or as bedded deposits.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges. Modernly used in construction aggregate and occasionally as a gemstone or for lighting fires (flint).
Geological facts
Chert has been used by humans for over 2 million years. Flint is a specific dark variety of chert. When struck against steel, chert can produce sparks, making it essential for early fire-starting tools.
Field identification & locations
Identify by its hardness (scratches glass), waxy appearance, and conchoidal (shell-like) fracture patterns. Commonly found in sedimentary basins and as river pebbles.
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary