sedimentary

Weathered iron-rich limestone or marl

Calcitic carbonate rock with limonite/goethite and clay impurities (predominantly CaCO₃)

AI-generated identification · may be incorrect

Hardness roughly 3–5, depending on impurities; tan, ochre, brown, gray, and blue-gray mottling; dull to earthy luster; fine-grained, massive texture with irregular fractures and possible thin bedding. Calcite-rich areas should fizz with dilute hydrochloric acid or strong vinegar, while iron-stained parts may not.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely deposited as carbonate-rich sediment, then compacted and variably altered by groundwater oxidation, producing yellow-brown iron oxides and green-gray clay/mineral zones. The photograph cannot establish a precise geological age; such rocks are widespread in the Neogene and Mesozoic sedimentary terrains around central Croatia.

Uses & applications

Mostly used locally as aggregate, road stone, or informal decorative material; attractive pieces may be collected, but it is generally not a gemstone and has low commercial value.

Geological facts

The vivid rusty colors usually reflect limonite/goethite coatings or cement. Blue-green areas may be clay minerals or copper-bearing alteration, but copper minerals cannot be confirmed visually.

Field identification & locations

Its angular broken surface and earthy coloration support a weathered sedimentary rock rather than a crystal or meteorite. Test acid reaction, streak (iron oxides commonly leave yellow-brown streak), density, and any visible bedding; avoid assuming metallic copper without chemical testing.