sedimentary

Banded Chert (Jasper)

Silicon Dioxide (SiO2) with iron oxide inclusions

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: Brown, tan, and dark green/grey bands; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Brown, tan, and dark green/grey bands
Luster: Waxy to dull

Identified June 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, often associated with Precambrian formations. The banding results from fluctuations in iron or clay content during deposition.

Uses & applications

Primarily used in lapidary work for cabochons and beads, as garden decor, and historically for stone tools due to its sharp fracture edges.

Geological facts

Banded chert specimens like this are often called 'ribbon chert'. They are extremely durable and can survive millions of years of river transport and erosion due to their high quartz content.

Field identification & locations

Identify in the field by its smooth, waxy texture and characteristic banding. Often found as stream-rounded river rocks or cobbles in glacial till and coastal beaches.