igneous
Iron-rich rock fragment, possibly weathered hematite-bearing basalt
Likely basalt with iron oxides/hydroxides; composition may include hematite (Fe₂O₃) or goethite (FeO(OH))
AI-generated identification · may be incorrectDark brown to black, fine-grained and opaque with dull to weakly metallic patches; basalt is typically Mohs 5–6, while hematite is about 5–6.5. The irregular fracture and rusty surface suggest weathering; crystal structure cannot be confirmed visually.
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Physical properties
Dark brown to black, fine-grained and opaque with dull to weakly metallic patches; basalt is typically Mohs 5–6, while hematite is about 5–6.5. The irregular fracture and rusty surface suggest weathering; crystal structure cannot be confirmed visually.
Formation & geological history
Possibly a mafic volcanic fragment formed from rapidly cooled lava, later altered by oxidation and weathering. Its precise geological age and identity cannot be determined from the photograph alone.
Uses & applications
Usually a common field specimen with little commercial value; iron-rich material may be collected for study, while basalt is used widely as aggregate, road stone, and construction material.
Geological facts
A reddish-brown streak would support hematite, whereas goethite commonly produces a yellow-brown streak. Strong attraction to a magnet would suggest magnetite or another iron-rich phase.
Field identification & locations
Common in volcanic and iron-rich terrains worldwide; inspect for vesicles, visible crystals, a rusty streak, and magnetic response. A streak test, magnet test, hardness test, and density measurement would improve identification.
