sedimentary

Banded Chert Pebble

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Hardness: 6.5-7 on Mohs scale; Color: Dark grey to black with brownish-tan quartz/chalcedony veins and banding; Luster: Waxy to sub-vitreous; Structure: Cryptocrystalline/microcrystalline; Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Luster: Waxy to sub-vitreous

Identified July 24, 2026More sedimentary →

Explore Banded Chert Pebble in the encyclopedia →

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 biogenic sediments (such as radiolarian shells or diatoms) or precipitation from hydrothermal fluids. Stream-tumbled and smoothed in riverbed environments over geological timescales.

Uses & applications

Historically used for stone tools and fire-starting due to its hardness and sharp conchoidal fracturing. Modern usage includes decorative landscaping, aquariums, lapidary polishing, and tumbled rock collections.

Geological facts

Chert is extremely durable and chemically resistant. Black varieties are often called basanite or touchstone, historically used by goldsmiths to test the purity of precious metals by observing the streak color.

Field identification & locations

Identified by its high hardness (scratches glass), waxy luster, smooth rounded pebble shape, and distinct yellowish/tan veining running through a dark matrix. Commonly found along riverbeds, gravel bars, and beaches.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sedimentary Sandstone

Arenite (Sedimentary Rock)

sedimentary

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Shale

Shale (clastic sedimentary rock)

sedimentary

Shale

Argillaceous sedimentary rock

sedimentary

Mudstone

Argillite / Siliciclastic sedimentary rock

sedimentary