sedimentary

Hardpan Nodule / Ferruginous Sandstone

Ferruginous Sandstone (Fe-cemented sediment)

AI-generated identification · may be incorrect

Hardness: 3-5 (varies by cementation); Color: Rusty brown, dull gray, or ochre; Luster: Dull or earthy; Structure: Granular with concretionary or pipe-like forms; Specific Gravity: 2.5-3.5.

Hardness: 3-5 (varies by cementation)
Color: Rusty brown, dull gray, or ochre
Luster: Dull or earthy

Identified June 30, 2026More sedimentary →

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Physical properties

Hardness: 3-5 (varies by cementation); Color: Rusty brown, dull gray, or ochre; Luster: Dull or earthy; Structure: Granular with concretionary or pipe-like forms; Specific Gravity: 2.5-3.5.

Formation & geological history

Formed by the precipitation of iron oxides (goethite/limonite) within sedimentary layers, typically in water-saturated environments or transition zones between soil layers. The specimen shows characteristic 'tube' formation often caused by mineralization around organic matter or water flow paths. Common in Quaternary deposits in the Baltic region.

Uses & applications

Generally used as a low-grade aggregate or for historical building stone in some regions. Primarily of interest as a geological curiosity for collectors.

Geological facts

These nodules are common in the Leningrad Oblast and surrounding Baltic areas, often found in glacial till or river banks. They are sometimes mistaken for meteorites or artifacts due to their unusual shapes and heavy iron content.

Field identification & locations

Check for a rusty or earthy streak (brown/yellowish). Look for the 'pipe' or hollow core structure. Found frequently in river beds or areas with high clay and iron-rich groundwater near Saint Petersburg.