Magnetite
Magnetite (Member of the Spinel Group) · Mineral Specimen / Industrial Mineral / Collector Mineral
Crystal System
Cubic (Isometric); habit is typically octahedral, dodecahedral, or massive/granular as seen in this specimen.
Mineral Group
Oxides (Spinel Group)
Chemical Formula
Fe2+Fe3+2O4 (Iron(II,III) oxide)
Formation Process
Primarily magmatic (late-stage crystallization) or metamorphic (contact or regional), also occurs in hydrothermal veins and as detrital sediment.
About This Crystal
An opaque, heavy mineral with a dull to metallic sub-metallic luster. The specimen shown is a dark grey-black, massive to granular chunk with irregular fracture and hints of octahedral crystal faces.
Physical Characteristics
Color: Iron-black to dark grey; Streak: Black; Cleavage: None (distinct parting on {111}); Fracture: Subconchoidal to uneven; Specific Gravity: 5.1-5.2; Magnetism: Strongly magnetic (lodestone is the naturally magnetized variety).
Optical Properties
Opaque; Refractive Index: N/A (metallic mineral); Reflected light shows a grey-white color; Isotropic.
Hardness & Durability
Origin Region
Kiruna (Sweden), South Africa, Russia, and USA (Utah/New York). Common in igneous, metamorphic, and sedimentary environments.
Hardness & Durability
Mohs Hardness: 5.5 - 6.5; Brittle tenacity; stable under normal conditions but can oxidize to hematite or limonite over geological time.
Care & Maintenance
Keep dry to prevent oxidation; clean with soft brush or dry cloth. Avoid ultrasonic cleaners and harsh chemicals. Store away from electronic devices due to magnetic field.
Rarity & Value
Very Common. While abundant as an ore of iron, well-formed octahedral crystals are valued by collectors. Generally inexpensive unless in high-quality crystal form.
Special Characteristics
Strongly magnetic; naturally occurring magnets are called Lodestones. High specific gravity makes it feel much heavier than it looks.
Lore & History
Historically used by early navigators in the form of Lodestone for the first compasses. In traditional lore, it is used for grounding, 'attracting' goals, and balancing polarities.