igneous
Iron-rich river pebble (likely weathered basalt or ironstone)
Indeterminate; possibly ferruginous basalt, hematite-rich ironstone, or limonite-coated mafic rock
AI-generated identification · may be incorrectDark reddish-brown, fine-grained, dull to earthy luster, rounded and smooth from abrasion, with small pits and a fracture-like groove. Estimated hardness is about 5–6 if basaltic, or 3–6 if substantially limonitic; no visible crystals or cleavage.
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Physical properties
Dark reddish-brown, fine-grained, dull to earthy luster, rounded and smooth from abrasion, with small pits and a fracture-like groove. Estimated hardness is about 5–6 if basaltic, or 3–6 if substantially limonitic; no visible crystals or cleavage.
Formation & geological history
Likely formed as a volcanic or iron-rich rock and later chemically weathered and rounded in a stream or shoreline environment. Precise geological age and identity cannot be determined from the photograph alone.
Uses & applications
Common specimens have little industrial or jewelry use, though crushed basalt is aggregate and ironstone can be an iron ore. Mainly of interest as a local pebble or teaching specimen.
Geological facts
The reddish-brown color commonly reflects iron oxides such as hematite and goethite coating or replacing the original rock. A streak test and magnet test would substantially improve identification.
Field identification & locations
Look for a red-brown to yellow-brown streak, density, magnetism, and whether the interior is black, gray, or rusty; basalt often shows tiny dark crystals, while ironstone is heavier and more uniformly rusty. Common in stream gravels and weathered iron-rich terrains.
