mineral
Tumbled dark metallic mineral specimen
Likely hematite or magnetite; identification is uncertain from the photograph
AI-generated identification · may be incorrectSmall, rounded, dark gray-black piece with a metallic to submetallic luster and irregular fracture. Hematite has Mohs hardness 5–6.5 and reddish-brown streak; magnetite has hardness 5.5–6.5 and is strongly magnetic.
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Physical properties
Small, rounded, dark gray-black piece with a metallic to submetallic luster and irregular fracture. Hematite has Mohs hardness 5–6.5 and reddish-brown streak; magnetite has hardness 5.5–6.5 and is strongly magnetic.
Formation & geological history
Iron oxides formed in hydrothermal veins, igneous rocks, or sedimentary iron formations over geologic time. Tumbled edges indicate human polishing or abrasion.
Uses & applications
Hematite is used as an iron ore, pigment, and jewelry stone; magnetite is an important iron ore and industrial mineral. Common tumbled pieces are mainly collectible.
Geological facts
A streak test is especially diagnostic: hematite leaves a red to reddish-brown streak, while magnetite leaves a black streak. Magnetite should attract a strong magnet; hematite generally does not, though some specimens are weakly magnetic.
Field identification & locations
Common localities include Brazil, Australia, India, South Africa, and the United States. Test magnetism and streak on unglazed porcelain; avoid relying on appearance alone because polished slag and other metallic minerals can look similar.
