sedimentary
Chert (Yellow Jasper variant)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Yellowish-brown with white inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (has conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Yellowish-brown with white inclusions
- 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 scale); Color: Yellowish-brown with white inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (has conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the precipitation of silica from groundwater or the accumulation of siliceous organisms in marine environments. This specimen appears to be a water-worn river pebble, likely dating from various sedimentary epochs depending on local geology.
Uses & applications
Historically used for stone tools due to its sharp edges when fractured. Modern uses include decorative gravel, lapidary work (if polished), and as a minor gemstone (jasper).
Geological facts
Yellow chert/jasper is often colored by the presence of goethite or limonite (iron oxides). Because it is harder than glass and steel, it was a primary material for prehistoric 'flintknapping' to create scrapers and arrowheads.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), waxy feel, and smooth, curved (conchoidal) breakage patterns. Typically found in riverbeds, glacial till, or as nodules within limestone/chalk formations.
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