Magnetite with Limonite
Magnetite (Iron Oxide) with Limonite coating · Mineral Specimen / Industrial Mineral
Crystal System
Cubic (Isometric); typically octahedral habit, though this specimen is massive
Mineral Group
Oxides (Spinel Group)
Chemical Formula
Fe2+Fe3+2O4 (Magnetite) / FeO(OH)·nH2O (Limonite)
Formation Process
Igneous magmatic segregation or contact metamorphism in iron-rich environments
About This Crystal
Opaque, dark grey to black mass with a sub-metallic to dull luster. Shows yellowish-brown earthy patches of secondary limonite oxidation.
Physical Characteristics
Black color, black streak, no cleavage, conchoidal to uneven fracture, SG 5.17, strongly magnetic, brittle tenacity
Optical Properties
Opaque; metallic to sub-metallic luster; non-pleochroic; isometric minerals are isotropic
Hardness & Durability
Origin Region
Global; notably Kiruna (Sweden), Adirondack Mts (USA), and various banded iron formations
Hardness & Durability
Mohs 5.5 - 6.5; brittle toughness; stable but prone to oxidation (rusting) in humid conditions
Care & Maintenance
Keep dry to prevent oxidation; clean with a soft dry brush; avoid acids and harsh chemicals
Rarity & Value
Common; primarily valued as an iron ore or for magnetic properties; low specimen value unless well-crystallized
Special Characteristics
Strongly ferrimagnetic; can act as a natural magnet (lodestone); provides a black streak on a porcelain plate
Lore & History
Historically used for early navigation as lodestones; traditionally associated with grounding and balancing energy centers