mineral
Magnetite / Hematite (Iron Ore Pebble)
Fe3O4 (Magnetite) / Fe2O3 (Hematite)
Hardness: 5.5-6.5 on the Mohs scale. Color: Dark metallic brownish-black to black. Luster: Metallic to submetallic, weathered surface. Crystal Structure: Isometric (Magnetite) or Trigonal (Hematite), though river-worn in this specimen. Specific Gravity: High (4.9-5.3 g/cm³), making it noticeably heavy for its size.
- Hardness
- 5
- Color
- Dark metallic brownish-black to black
- Luster
- Metallic to submetallic, weathered surface
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Physical properties
Hardness: 5.5-6.5 on the Mohs scale. Color: Dark metallic brownish-black to black. Luster: Metallic to submetallic, weathered surface. Crystal Structure: Isometric (Magnetite) or Trigonal (Hematite), though river-worn in this specimen. Specific Gravity: High (4.9-5.3 g/cm³), making it noticeably heavy for its size.
Formation & geological history
Formed in banded iron formations (BIFs), igneous intrusions, or contact metamorphic environments. This rounded cobble shape indicates extensive weathering and erosion in a river bed or coastal environment.
Uses & applications
Primary ore for iron and steel production. Highly collected as heavy mineral specimens, decorative river stones, and magnetic specimens.
Geological facts
Stream-rounded iron ore pebbles often retain high magnetism if rich in magnetite. The natural erosion process smoothens the exterior while exposing faint internal fracture patterns or metallic sheen.
Field identification & locations
Check for strong attraction to a magnet (magnetite) or perform a streak test on unglazed porcelain (red-brown for hematite, black for magnetite). Frequently found in alluvial deposits downstream from iron-rich geologic formations.
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