sedimentary

Banded Chert (Jasper) River Pebble

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Tan, brown, and grey banding; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Tan, brown, and grey banding
Luster: Waxy to dull

Identified June 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, brown, and grey banding; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Formation & geological history

Formed as a chemical precipitate or through the replacement of limestone by silica-rich fluids. This specimen is a water-worn pebble, likely eroded from ancient sedimentary beds and smoothed over thousands of years in a river environment.

Uses & applications

Commonly used as decorative gravel, in lapidary work (polishing and tumbling), and historically used by indigenous people for stone tools due to its sharp fracture edges.

Geological facts

Chert and Jasper are varieties of chalcedony. The banding is often caused by the rhythmic precipitation of iron oxides or other impurities during the silica deposition process.

Field identification & locations

Identify in the field by its smooth texture, hardness (it will scratch glass), and characteristic banding. Often found in riverbeds, glacial tills, or coastal beaches.