mineral
Tumbled metallic-gray stone, likely hematite or magnetite
Hematite (Fe₂O₃) or magnetite (Fe₃O₄); exact identification requires testing
AI-generated identification · may be incorrectDark gray to black, metallic-to-submetallic luster, opaque, fine-grained and smoothly tumbled. Hematite has Mohs hardness 5–6.5 and a reddish-brown streak; magnetite has hardness 5.5–6.5 and is strongly magnetic, with no visible cleavage.
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Physical properties
Dark gray to black, metallic-to-submetallic luster, opaque, fine-grained and smoothly tumbled. Hematite has Mohs hardness 5–6.5 and a reddish-brown streak; magnetite has hardness 5.5–6.5 and is strongly magnetic, with no visible cleavage.
Formation & geological history
These iron oxides form in hydrothermal, igneous, metamorphic, and sedimentary environments; their formation spans much of Earth’s geological history. The rounded shape indicates human tumbling or polishing.
Uses & applications
Used as iron ore, pigment, abrasive, and ornamental material; polished hematite is common in inexpensive jewelry and metaphysical collections. Magnetite is also used in industrial magnetic applications.
Geological facts
A streak test is more diagnostic than appearance: hematite leaves a red to reddish-brown streak, while magnetite leaves a black streak. A strong attraction to a magnet strongly favors magnetite.
Field identification & locations
Common sources include Brazil, South Africa, Australia, the United States, and Canada. Test magnetism and streak on unglazed porcelain; avoid scratching valuable surfaces.
