fossil

Silicified fossil-bearing chert

Microcrystalline quartz (SiO₂), likely chalcedony replacing carbonate shell material

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque cream, tan, brown, and gray; waxy to dull luster; no visible cleavage; conchoidal fracture; fossil cavities and shell-like forms are apparent. Specific gravity is typically 2.5–2.7.

Identified September 7, 2026More fossil →

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At a glance

Common name: Silicified fossil-bearing chert
Scientific name: Microcrystalline quartz (SiO₂), likely chalcedony replacing carbonate shell material
Category: fossil
Identified: September 7, 2026
Method: Standard

AI Estimated Value

Approximately $10–$50 for a common rough specimen; $50–$150 or more if the fossil identity, locality, preservation, or polish is exceptional.

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

Silica-rich groundwater replaced or filled a carbonate fossil, producing silicified limestone/chert during diagenesis. Exact geological age and locality cannot be determined from the photograph alone.

Uses & applications

Primarily a collector specimen, teaching sample, or lapidary material; selected pieces may be polished for display, cabochons, or ornamental objects, but this specimen appears relatively rough.

Geological facts

The rounded internal forms may represent replaced shells or other fossil structures, with translucent chalcedony and iron-oxide staining. Silicification commonly preserves fine fossil details while making the specimen much harder than the original limestone.

Field identification & locations

Look for waxy translucent silica, conchoidal breaks, hardness sufficient to scratch glass, and recognizable fossil outlines; it is commonly found in sedimentary basins and fossil-bearing limestones worldwide. Avoid acid testing unless a small surface is available, because exposed carbonate may effervesce while silica will not.