sedimentary

Flint/chert fragment (likely weathered chert nodule)

Microcrystalline quartz (SiO₂), commonly chalcedony with possible calcite or iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; pale cream interior with a dark gray-brown weathered cortex, dull to waxy luster, cryptocrystalline structure, and conchoidal fracture rather than cleavage. The rounded exterior suggests natural abrasion or a nodule surface.

Identified August 30, 2026More sedimentary →

Explore Flint/chert fragment (likely weathered chert nodule) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

At a glance

Common name: Flint/chert fragment (likely weathered chert nodule)
Scientific name: Microcrystalline quartz (SiO₂), commonly chalcedony with possible calcite or iron-oxide staining
Category: sedimentary
Identified: August 30, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 as an ordinary fragment; attractive patterned or tool-quality specimens may sell for $10–$50.

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

Forms when silica-rich groundwater replaces or fills pores in limestone, chalk, or other sediments, commonly during diagenesis; the exact age cannot be determined from the photograph. Chert occurs from Precambrian to modern sedimentary environments.

Uses & applications

Used historically for sharp-edged tools and fire-starting, and today mainly for lapidary work, study, and collecting; rarely used as aggregate.

Geological facts

Fresh fractures are typically glassy and sharply conchoidal, while weathered surfaces become brown, gray, or cream. A steel file generally will not scratch true chert, whereas chert can scratch ordinary glass.

Field identification & locations

Common in limestone, chalk, gravel beds, glacial till, and stream deposits worldwide, especially England, France, the Great Lakes region, and Texas. Confirm with a fresh edge, glass-scratch test, and inspection for waxy texture; the image alone cannot exclude a similar siliceous rock.