sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, tan, and grey/green; Luster: Waxy to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65
- Hardness
- 6
- Color
- Variegated brown, tan, and grey/green
- 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: Variegated brown, tan, and grey/green; Luster: Waxy to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65
Formation & geological history
Formed through the accumulation of silica-rich fluids in sedimentary environments or the replacement of organic/calcite materials. This specimen appears as a river-worn or water-smoothed nodule, common in various geological ages.
Uses & applications
Historically used for making stone tools (arrowheads/scrapers); currently used for lapidary work, jewelry (cabochons), and as a decorative stone in landscaping.
Geological facts
Chert is so hard it can strike sparks against steel, making it a primary fire-starting tool for ancient civilizations. It is a dense, opaque variety of chalcedony.
Field identification & locations
Identify by its extreme hardness (will scratch glass), waxy feel when polished, and distinctive shell-like (conchoidal) fracture pattern. Commonly found in stream beds or gravel pits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary