sedimentary

Banded Chert (or Banded Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored bands (brown, olive, tan, red); Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Multi-colored bands (brown, olive, tan, red)
Luster: Waxy to vitreous

Identified June 27, 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 through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids in marine environments. The banding represents changes in sediment composition or oxygen levels during deposition.

Uses & applications

Used for lapidary work, jewelry making (cabochons), flint-knapping for primitive tools, and as decorative landscape stones.

Geological facts

Commonly known as 'Wonderstone' in some regions when the banding is particularly rhythmic. In ancient times, varieties of banded chert were highly prized for creating sharp-edged cutting tools and arrowheads due to their predictable fracturing.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife), smooth waxy texture, and distinct layers. Often found in riverbeds, glacial tills, or as nodules within limestone formations.

Other sedimentary specimens

See all

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

Arenite (primarily SiO2)

sedimentary

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary