sedimentary

Weathered chert or silicified limestone nodule

Microcrystalline quartz (SiO₂), possibly replacing limestone; exact identification requires testing

AI-generated identification · may be incorrect

Cream to tan, dense and fine-grained with a dull-to-waxy luster and irregular solution cavities. Likely hardness about 6.5–7 if chert; limestone would be 3 and fizz strongly with dilute hydrochloric acid. No obvious crystal faces or cleavage are visible.

Identified August 9, 2026More sedimentary →

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At a glance

Common name: Weathered chert or silicified limestone nodule
Scientific name: Microcrystalline quartz (SiO₂), possibly replacing limestone; exact identification requires testing
Category: sedimentary
Identified: August 9, 2026
Method: Standard

AI Estimated Value

$1–$10 as a common field specimen; up to about $15–$30 if unusually attractive, fossiliferous, or well polished.

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 in marine sedimentary rocks as silica-rich material or a silicified limestone concretion, later exposed and rounded by weathering. East Texas near 31.6°N, 95.6°W is dominated by sedimentary formations, making this interpretation regionally plausible; it is not an obvious igneous rock.

Uses & applications

Chert is used historically for sharp tools and occasionally aggregate; limestone is used for cement, lime, roadstone, and construction. This specimen has modest decorative or educational value rather than gemstone value.

Geological facts

The cavities may be weathered fossil, shell, or mineral-remnant spaces. Silicification can preserve textures while replacing the original carbonate.

Field identification & locations

Try a fresh edge: chert can scratch glass, while limestone usually cannot. Apply a drop of vinegar or dilute hydrochloric acid to a concealed spot—vigorous fizz indicates calcite-rich limestone, while no fizz supports chert or silicification. Commonly found as nodules or weathered fragments in regional sedimentary deposits.