mineral
Possible hematite-rich ironstone or magnetite-bearing specimen
Likely hematite (Fe₂O₃), magnetite (Fe₃O₄), or an iron-rich slag-like geological specimen
AI-generated identification · may be incorrectBlack to dark gray, strongly metallic to submetallic luster, irregular botryoidal/rough surface, and massive structure. Hematite has Mohs hardness 5–6.5 and reddish-brown streak; magnetite has hardness 5.5–6.5 and a black streak, and is magnetic.
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Physical properties
Black to dark gray, strongly metallic to submetallic luster, irregular botryoidal/rough surface, and massive structure. Hematite has Mohs hardness 5–6.5 and reddish-brown streak; magnetite has hardness 5.5–6.5 and a black streak, and is magnetic.
Formation & geological history
Iron oxides form through hydrothermal alteration, weathering, or precipitation in sedimentary iron deposits; magnetite commonly crystallizes in igneous and metamorphic environments. Age depends on locality and cannot be determined photographically.
Uses & applications
Used as an iron ore, pigment, polishing abrasive, and collector specimen; attractive polished pieces may be decorative. A magnet and streak test are needed to distinguish it from industrial slag.
Geological facts
Magnetite is naturally magnetic, while hematite is usually weakly magnetic or nonmagnetic. The visible rounded, highly textured form could also represent botryoidal hematite or weathered ironstone.
Field identification & locations
Common in banded iron formations, volcanic districts, hydrothermal veins, and heavily weathered iron-rich soils worldwide. Check magnetism, streak color, density, and whether bubbles or glassy areas suggest slag rather than natural material.
