mineral
Magnetite or Ironstone Nodule
Magnetite (Fe3O4) or Hematite-rich Sedimentary Nodule
Hardness: 5.5-6.5; Color: Dark brown to black; Luster: Dull to metallic; Streak: Black or reddish-brown; Structure: Granular or massive; Magnetic properties often present.
- Hardness
- 5
- Color
- Dark brown to black
- Luster
- Dull to metallic
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Physical properties
Hardness: 5.5-6.5; Color: Dark brown to black; Luster: Dull to metallic; Streak: Black or reddish-brown; Structure: Granular or massive; Magnetic properties often present.
Formation & geological history
Formed through the oxidation of iron-bearing minerals or as sedimentary concretions in iron-rich environments. Common in metamorphic belts and sedimentary iron formations.
Uses & applications
Major ore of iron; used in heavy industry, construction materials, and as magnetic media. Small nodules are mainly of interest to amateur geologists and collectors.
Geological facts
Magnetite is the most magnetic of all the naturally-occurring minerals on Earth. It was used by ancient navigators as a 'lodestone' to determine direction.
Field identification & locations
Identify by testing with a magnet (it will likely be attracted) and checking the streak color by rubbing it on unglazed porcelain. Commonly found in stream beds or eroded soil.
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