sedimentary

Banded chert (likely jasper/chert pebble)

Microcrystalline quartz, SiO₂, with iron-oxide and clay/mineral impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; tan, gray, cream, and brown wavy bands; dull to waxy luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The rounded shape indicates natural abrasion or tumbling.

Identified September 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from silica-rich marine or groundwater deposits that recrystallized into chert, with later iron-oxide staining and layered sedimentary banding; exact age and locality cannot be determined from the photograph.

Uses & applications

Used as decorative stone, cabochons, beads, and lapidary material; historically, chert was knapped for tools and fire-starting. Common pieces have modest collector value.

Geological facts

Its fine quartz texture can produce sharp conchoidal edges when broken, unlike most granular sandstone. The attractive layers may also be described commercially as banded jasper, though “jasper” is an opaque variety of microcrystalline quartz.

Field identification & locations

Look for a glassy or waxy surface, high scratch resistance, opaque layered colors, and conchoidal fracture; it should scratch ordinary glass but not be scratched by a steel knife. Common in sedimentary terrains, gravel beds, and river deposits worldwide.