igneous
Iron-rich weathered rock, likely limonite-bearing basalt or ironstone
Fine-grained mafic rock with iron oxides/hydroxides; probable basalt altered to limonite/goethite
AI-generated identification · may be incorrectDark gray-brown, dull to earthy luster, irregular massive texture, and rusty orange surface staining. Estimated hardness 5–6 for the unweathered matrix and lower where limonite is abundant; cleavage is absent and specific gravity is roughly 2.8–3.5.
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Physical properties
Dark gray-brown, dull to earthy luster, irregular massive texture, and rusty orange surface staining. Estimated hardness 5–6 for the unweathered matrix and lower where limonite is abundant; cleavage is absent and specific gravity is roughly 2.8–3.5.
Formation & geological history
Likely formed as basaltic lava that cooled rapidly, then underwent prolonged oxidation and groundwater alteration, producing goethite/limonite coatings. The exact geological age cannot be determined from the photograph.
Uses & applications
Usually collected as a field specimen or used as low-grade iron ore; it has little jewelry or construction value unless part of a distinctive locality or unusually high-grade ironstone.
Geological facts
The orange-brown coloration reflects ferric iron minerals rather than metallic native iron. A streak test, magnet test, and fresh-surface examination would substantially improve identification.
Field identification & locations
Common in weathered basalt terrains, iron-rich soils, and gossans above sulfide deposits. Check for a yellow-brown streak, weak magnetism, and a sparkly or metallic fresh face; these help distinguish it from slag or ordinary sandstone.
