sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Opaque brown, yellowish-tan, and earthy orange; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Hardness: 6
Color: Opaque brown, yellowish-tan, and earthy orange
Luster: Dull to waxy

Identified June 12, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed primarily through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. This specific river-worn pebble suggests secondary transportation and rounding via water erosion.

Uses & applications

Historically used for stone tools due to its conchoidal fracture. Currently used for lapidary work, landscaping, and as a collector specimen.

Geological facts

Chert and jasper are among the oldest materials used by humans to create sharp-edged tools. When struck with steel, it can create sparks, making it useful for fire-starting.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife), smooth waxy feel when wet, and characteristic curved (conchoidal) breaks. Commonly found in riverbeds, glacial tills, and sedimentary basins worldwide.