sedimentary

Likely weathered chert or flint nodule

Microcrystalline quartz (SiO₂), possibly chalcedony-rich chert

AI-generated identification · may be incorrect

Dark gray to brown, dull-to-waxy luster, rounded nodule with a lighter weathering rind and pale speckles. Hardness about 7 Mohs; conchoidal fracture; no obvious cleavage; specific gravity roughly 2.6.

Identified September 6, 2026More sedimentary →

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At a glance

Common name: Likely weathered chert or flint nodule
Scientific name: Microcrystalline quartz (SiO₂), possibly chalcedony-rich chert
Category: sedimentary
Identified: September 6, 2026
Method: Standard

AI Estimated Value

About $1–$10 for a common nodule; $10–$30 if unusually attractive, polished, or strongly patterned. Identification is provisional because the image does not show a fresh fracture or scale.

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

Chert forms when silica replaces or fills pores in sedimentary rocks, commonly limestone or chalk, during diagenesis. The rounded shape suggests erosion and transport; its exact geological age cannot be determined from the photograph.

Uses & applications

Used historically for sharp tools and fire-starting, and occasionally as decorative or lapidary material. Ordinary nodules generally have little commercial value.

Geological facts

The dark interior and lighter rind are typical of flint/chert weathering. A fresh break should be curved and glassy rather than granular.

Field identification & locations

Consistent with sedimentary terrains around the lower Volga region near 48.5°N, 44.5°E, where transported chert and flint nodules can occur. Test carefully with a steel file or glass: genuine chert should scratch ordinary glass; avoid striking unknown specimens because sharp flakes can form.