sedimentary
Chert (Jasper)
Sedimentary Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish-orange; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brown, tan, reddish-orange
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Jasper) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish-orange; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids. This specimen appears water-worn, suggesting it was transported by a river or stream.
Uses & applications
Historically used for stone tools (flintknapping); currently used in landscaping, as aquarium decor, or polished for lapidary art and jewelry.
Geological facts
Chert is so hard it can scratch steel and was used by prehistoric humans to create sharp spearheads and knives due to its predictable conchoidal fracturing.
Field identification & locations
Identify in the field by its smooth, waxy feel, conchoidal (shell-like) fractures, and its ability to scratch glass. Commonly found in riverbeds or as nodules within limestone.
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