mineral
Tumbled hematite (likely hematite-rich ironstone)
Hematite, Fe₂O₃; possibly mixed with magnetite or goethite
AI-generated identification · may be incorrectDark steel-gray to black, metallic-to-submetallic luster, uneven/conchoidal fracture, and hardness about 5–6.5 Mohs; hematite has a reddish-brown streak, while magnetite is strongly magnetic.
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Physical properties
Dark steel-gray to black, metallic-to-submetallic luster, uneven/conchoidal fracture, and hardness about 5–6.5 Mohs; hematite has a reddish-brown streak, while magnetite is strongly magnetic.
Formation & geological history
Forms by oxidation and precipitation of iron in hydrothermal, sedimentary, or metamorphic environments, commonly in Precambrian banded iron formations. The rounded shape appears human-tumbled or naturally water-worn.
Uses & applications
Used as an iron ore, pigment, polishing material, and ornamental stone; polished hematite is also used in inexpensive jewelry and carvings.
Geological facts
Despite its black appearance, hematite typically produces a red to reddish-brown streak. The specimen’s very dark color and glossy surface could indicate magnetite-bearing hematite, but the image cannot confirm this.
Field identification & locations
Test with an unglazed ceramic streak plate: hematite leaves red-brown powder; magnetite leaves black streak and attracts a magnet. Common localities include Brazil, Australia, India, South Africa, and the United States.
