sedimentary
Chert (Yellow Jasper/Flint pebble)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Yellow, tan, and dark grey/black; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Yellow, tan, and dark grey/black
- 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: Yellow, tan, and dark grey/black; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. These rounded pebbles often originate from ancient riverbeds or coastal deposits where they have been smoothed by water erosion.
Uses & applications
Historically used for stone tools (arrowheads). Modern uses include landscaping, tumbling for hobbyists, and industrial abrasives. High-quality specimens are used in lapidary work.
Geological facts
Chert and its varieties like Jasper are known for their conchoidal fracture, meaning they break with smooth, curved surfaces. This made them essential for prehistoric tool making.
Field identification & locations
Identify by its hardness (it will scratch glass) and waxy luster when wet or polished. Often found in river gravels and on beaches. Look for the smooth, rounded surface indicating water transport.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary