Magnetite with Limonite
Magnetite (Iron Oxide) · Mineral Specimen / Industrial Iron Ore
Crystal System
Cubic (Isometric); habit often octahedral, dodecahedral, or massive granular.
Mineral Group
Oxides (Spinel Group)
Chemical Formula
Fe2+Fe3+2O4
Formation Process
Primarily Igneous (magmatic segregation) or Metamorphic (contact or regional metamorphism of iron-rich sediments); also found in Hydrothermal veins.
About This Crystal
Opaque, metallic to sub-metallic black mineral with silver-grey highlights. Shows a granular or massive texture in this specimen, with brownish-yellow oxidation crusts of Limonite. Luster is metallic on fresh surfaces.
Physical Characteristics
Color: Iron-black. Streak: Black. Cleavage: None (shows octahedral parting). Fracture: Subconchoidal to uneven. Specific Gravity: 5.1-5.2. Strongly magnetic (ferrimagnetic).
Optical Properties
Opaque (does not transmit light). In reflected light microscopy, it is greyish-white and isotropic.
Hardness & Durability
Origin Region
Common worldwide; notable deposits in Kiruna (Sweden), Adirondack Mountains (USA), and various localities in Brazil and South Africa.
Hardness & Durability
Mohs hardness: 5.5 to 6.5. Toughness is brittle. Stable under normal conditions but reactive to strong acids.
Care & Maintenance
Keep dry to prevent further oxidation into limonite/hematite. Clean with a soft brush; avoid water or ultrasonic cleaners if the specimen is porous or combined with loose matrix.
Rarity & Value
Very common. Low value for small massive specimens; higher value for well-defined octahedral crystals or 'lodestone' varieties with natural polarity.
Special Characteristics
Strong magnetism is its most defining trait. This specimen shows yellow-brown 'limonite' staining, representing the chemical weathering of the iron.
Lore & History
Historically used as the first compasses (lodestones) by early navigators. Metaphysically associated with grounding, manifestation, and balancing opposite polarities (yin/yang) due to its magnetic nature.