sedimentary

Silicified fossil-bearing limestone (likely chert/agate replacement)

Microcrystalline quartz (SiO₂) replacing carbonate rock; possible fossiliferous limestone

AI-generated identification · may be incorrect

Hardness about 6.5–7 where silicified; gray, cream, and yellow-brown colors, waxy to dull luster, massive texture, and no obvious cleavage. Irregular cavities and pale fossil-like markings are visible; yellow areas may be iron-oxide staining.

Identified August 10, 2026More sedimentary →

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At a glance

Common name: Silicified fossil-bearing limestone (likely chert/agate replacement)
Scientific name: Microcrystalline quartz (SiO₂) replacing carbonate rock; possible fossiliferous limestone
Category: sedimentary
Identified: August 10, 2026
Method: Standard

AI Estimated Value

About $5–$30 as an ordinary rough specimen; $30–$100+ if verified fossil textures, attractive patterning, or good polish are present.

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

Probably formed when silica-rich groundwater replaced or infilled a marine limestone, preserving fossil textures; the original carbonate may be Paleozoic–Mesozoic, but its exact age cannot be determined from the image. Common in sedimentary basins, nodular chert beds, and weathered limestone exposures.

Uses & applications

Used as a decorative or lapidary stone when attractive; otherwise mainly a field or fossil/mineral specimen. It may take a polish if sufficiently silicified.

Geological facts

The specimen appears to contain possible shell or trace-fossil impressions, but confirmation requires close examination or cutting. Silicification can produce agate-like banding and greatly increase hardness relative to surrounding limestone.

Field identification & locations

Test a fresh edge with a steel knife and glass: quartz-rich material resists the knife and can scratch glass, whereas limestone fizzes with dilute hydrochloric acid. Common in limestone and chert regions worldwide; avoid acid if preservation is important.