sedimentary

Banded Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Highly variable with bands of red (iron-rich), tan, and white. Luster: Waxy to dull. Crystal structure: Cryptocrystalline (microscopic quartz). Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.7.

Hardness: 6
Luster: Waxy to dull

Identified January 24, 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 radiolarian or diatoms) or by chemical precipitation from hydrothermal fluids in sedimentary basins. The red banding specifically indicates high iron oxide content during deposition.

Uses & applications

Used primarily as decorative landscaping rock (as seen in the image), semi-precious gemstones for jewelry (cabochons), and historically for toolmaking (lithic flakes/arrowheads) due to its sharp conchoidal fracture.

Geological facts

Banded chert can range in age from the Precambrian to much more recent geological eras. Iron-rich versions are often referred to as Jasper. In the context of the photo (Likely Southwestern US/Arizona), these are common components of local alluvial gravels or tectonic deposits.

Field identification & locations

Identify in the field by its distinct hardness (will scratch glass), conchoidal fracture (smooth, curved breaks), and waxy sheen. Look for it in desert landscapes, riverbeds, and as ornamental stone in residential xeriscaping.