Magnetite
Magnetite (Oxide Mineral) · Mineral Specimen and Collector Mineral; also an important Iron Ore.
Crystal System
Cubic (Isometric); habit is typically octahedral or dodecahedral crystals, also occurs in massive, granular, or micaceous forms.
Mineral Group
Oxides (Spinel Group)
Chemical Formula
Fe2+Fe3+2O4 (Iron Oxide)
Formation Process
Primarily Igneous as an accessory mineral in mafic and ultramafic rocks, but also found in contact metamorphic deposits (skarns) and high-temperature hydrothermal veins.
About This Crystal
An opaque mineral with a dark grey to black color. It exhibits a metallic to sub-metallic luster on fresh surfaces, often becoming duller when weathered. It has a granular texture and a heavy, dense feel.
Physical Characteristics
Color: Iron-black to dark grey; Streak: Black; Cleavage: None (has octahedral parting); Fracture: Uneven to sub-conchoidal; Specific Gravity: 5.1-5.2; Tenacity: Brittle; Notable for being naturally magnetic.
Optical Properties
Opaque; Single Refraction (Isotropic). In reflected light, it appears grey-white with a brownish tint. No pleochroism or dispersion is visible due to opacity.
Hardness & Durability
Origin Region
Large deposits in Kiruna (Sweden), Pilbara (Australia), Brazil, and various locations in the USA including Adirondack Mountains and California.
Hardness & Durability
Mohs hardness: 5.5 to 6.5. Toughness is generally good, but it is brittle and can chip. Stable under most conditions but can oxidize to hematite or limonite over long periods in wet environments.
Care & Maintenance
Clean with a soft brush and warm soapy water; dry immediately to prevent rust-like oxidation. Store away from magnets (which can de-magnetize specimen) and electronic devices. Avoid harsh chemicals.
Rarity & Value
Common; Value is generally low for massive specimens but increases for well-formed octahedral crystals or 'Lodestone' (naturally magnetized variety).
Special Characteristics
Strongly ferrimagnetic; some specimens (Lodestones) act as natural magnets. Noted for its high density and black streak that distinguishes it from hematite (which has a red-brown streak).
Lore & History
Historically used in the first compasses (Lodestones) by ancient Greek and Chinese sailors. Metaphysically, it is traditionally believed to be a grounding stone that aligns the energies of the body with the Earth's magnetic field.