sedimentary
Chert pebble
Cryptocrystalline Quartz (SiO2)
Hardness: 7 Mohs scale; Color: Dark grey to greenish-grey with dark fracture veins; Luster: Waxy to dull; Crystal structure: Microcrystalline; Conchoidal fracture pattern.
- Hardness
- 7 Mohs scale
- Color
- Dark grey to greenish-grey with dark fracture veins
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs scale; Color: Dark grey to greenish-grey with dark fracture veins; Luster: Waxy to dull; Crystal structure: Microcrystalline; Conchoidal fracture pattern.
Formation & geological history
Forms through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by chemical precipitation in marine environments. This specimen has been rounded by fluvial or marine water action.
Uses & applications
Historically used for stone tools due to its sharp edges when broken; used today in landscaping, construction aggregate, and as a material for lapidary tumbling.
Geological facts
Chert is so hard it can scratch glass. It was one of the first materials used by early humans to create arrowheads and scrapers. The dark lines are often secondary silica-filled fractures or manganese dendrites.
Field identification & locations
Identify in the field by its extreme hardness, smooth waxy texture, and conchoidal (shell-like) fracture surfaces. Commonly found in riverbeds and on beaches.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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 (primarily SiO2)
sedimentary