sedimentary

Banded chert or siliceous sedimentary rock

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide staining and possible carbonate/clay layers

AI-generated identification · may be incorrect

Identified September 19, 2026More sedimentary →

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At a glance

Common name: Banded chert or siliceous sedimentary rock
Scientific name: Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide staining and possible carbonate/clay layers
Category: sedimentary
Identified: September 19, 2026
Method: Standard

AI Estimated Value

About $5–$25 as an ordinary hand specimen; $30–$100+ if unusually patterned, fossiliferous, locality-documented, or attractively polished.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Gray to olive-brown, fine-grained and dull to slightly waxy, with irregular tan-brown bands and fractures; hardness about 6.5–7 Mohs, no visible cleavage, conchoidal to uneven fracture, and typically specific gravity near 2.6. Exact identification is limited because the specimen appears weathered and may include multiple lithologies.

Formation & geological history

Likely formed from silica-rich sediment or chemical/biogenic silica that lithified and later fractured, with iron-bearing fluids producing the ochre bands; age cannot be determined from the photograph. The layered appearance could also indicate chert interbedded with shale or jasper.

Uses & applications

Used as a source of silica, aggregate, and historically for sharp-edged tools; attractive polished pieces are collected or used decoratively, though this specimen appears mainly of teaching or field-collecting interest.

Geological facts

Chert commonly preserves fossils or microscopic textures and can resemble jasper, silicified limestone, or fine-grained volcanic rock. A steel file generally will not scratch fresh chert, while the rock may scratch ordinary glass.

Field identification & locations

Common in sedimentary sequences worldwide, including limestone, chalk, and marine basin deposits. Test an unweathered surface for glassy conchoidal fracture and hardness; dilute acid can help detect any carbonate-rich layers.