igneous
Weathered iron-rich rock, possibly basalt or ironstone
Indeterminate; likely Fe-oxide-bearing basaltic rock (commonly magnetite/hematite in a silicate matrix)
AI-generated identification · may be incorrectDark reddish-brown, dull to weakly earthy luster, fine- to medium-grained, and apparently massive with no visible cleavage. Estimated hardness is about 5–6 if basaltic, or variable if heavily weathered; specific gravity may be moderately high from iron oxides.
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Physical properties
Dark reddish-brown, dull to weakly earthy luster, fine- to medium-grained, and apparently massive with no visible cleavage. Estimated hardness is about 5–6 if basaltic, or variable if heavily weathered; specific gravity may be moderately high from iron oxides.
Formation & geological history
Likely an iron-weathered volcanic rock or ironstone fragment formed through cooling of mafic lava and subsequent oxidation. Its geological age cannot be determined from the photograph.
Uses & applications
Ordinary fragments have little commercial value; basalt is used as aggregate and dimension stone, while hematite-rich material can be an iron ore if sufficiently concentrated.
Geological facts
The rusty coloration commonly results from hematite or limonite coating or replacing iron-bearing minerals. A magnet test can help detect magnetite, though weak attraction does not exclude basalt.
Field identification & locations
Common in volcanic terrains and areas with iron-rich weathering. Examine a fresh broken surface, test streak on unglazed porcelain, check magnetism, and use a hand lens; value is typically $1–$10 as an unexceptional specimen, potentially higher if unusually magnetic or mineralogically distinctive.
