sedimentary
Chert (Jasper influence)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Brownish-red to tan with earthy mottling. Luster: Dull to waxy. Crystal structure: Trigonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.65.
- Hardness
- 6
- Color
- Brownish-red to tan with earthy mottling
- Luster
- Dull to waxy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Brownish-red to tan with earthy mottling. Luster: Dull to waxy. Crystal structure: Trigonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic debris or chemical precipitation in marine or groundwater environments. This specimen appears weathered and stained with iron oxides (hematite/limonite).
Uses & applications
Historically used for stone tools/arrowheads. Modernly used in landscaping, as tumbling rough, or for decorative lapidary work.
Geological facts
Chert has been used by humans for hundreds of thousands of years due to its ability to maintains a sharp edge when fractured. Reddish varieties are often called Jasper.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its smooth, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds and limestone 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