sedimentary

Banded chert or silicified sedimentary stone

Microcrystalline quartz (chalcedony), SiO₂, possibly with iron-oxide and clay impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray-green to brown, dull to waxy luster, very fine-grained and cryptocrystalline, with no visible cleavage. The elongated shape and surface may reflect natural weathering or human shaping/polishing.

Identified August 23, 2026More sedimentary →

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At a glance

Common name: Banded chert or silicified sedimentary stone
Scientific name: Microcrystalline quartz (chalcedony), SiO₂, possibly with iron-oxide and clay impurities
Category: sedimentary
Identified: August 23, 2026
Method: Standard

AI Estimated Value

$5–$30 as a common specimen; approximately $30–$150 if confirmed as an archaeological artifact or unusually attractive patterned chert, subject to provenance and legality.

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

Formation & geological history

Likely formed when silica replaced or cemented fine sediment, potentially as chert in marine or volcanic-sedimentary beds; age cannot be determined from the photograph. Its tapered, symmetrical form could also indicate a worked stone tool, but the image alone cannot confirm manufacture.

Uses & applications

Chert is used historically for sharp-edged tools and occasionally as aggregate or decorative stone; attractive varieties may be collected or polished. It has limited jewelry value unless strongly patterned or gem-quality.

Geological facts

Freshly broken chert commonly shows a smooth conchoidal fracture and sharp edges. Green coloration may result from chlorite, epidote, or other mineral impurities, while brown tones commonly reflect iron oxides.

Field identification & locations

Look for a glassy, waxy surface, conchoidal fracture, lack of visible grains, and the ability to scratch ordinary glass. Common occurrences include limestone formations, nodules, river gravels, and hydrothermal environments worldwide.