Magnetite
Magnetite (IMA-approved mineral name) · Mineral Specimen / Industrial Mineral / Collector Mineral
Crystal System
Cubic (Isometric); typically forms as octahedral, dodecahedral, or massive habits. Twinning is common on the {111} plane (Spinel law).
Mineral Group
Oxides (Spinel Group; Inverse Spinel structure)
Chemical Formula
Fe2+Fe3+2O4 (Iron(II,III) oxide)
Formation Process
Primarily Igneous (magmatic segregation in basic rocks) and Metamorphic (contact or regional metamorphism). Also forms via hydrothermal veins and as detrital grains in sedimentary 'black sands'.
About This Crystal
An opaque, metallic mineral with a dark grey to black color. It commonly displays octahedral faces or massive granular textures. The specimen shown exhibits a metallic luster with subtle iridescent or 'greasy' patches on fractured surfaces.
Physical Characteristics
Color: Iron-black; Streak: Black; Cleavage: None (distinct octahedral parting may occur); Fracture: Subconchoidal to uneven; Specific Gravity: 5.17–5.18; Tenacity: Brittle; Magnetism: Strongly magnetic (Ferrimagnetic); Fluorescence: None.
Optical Properties
Opaque (singly refractive in reflected light). Refractive index is inapplicable for transmission; metallic reflectance is approximately 20%. No pleochroism or dispersion is visible to the naked eye.
Hardness & Durability
Origin Region
Kiruna (Sweden), Karangas (Russia), Adirondack Mts (USA), South Africa. Found in igneous, metamorphic, and sedimentary environments.
Hardness & Durability
Mohs Hardness: 5.5 to 6.5. Toughness is generally poor (brittle). It is stable under normal conditions but can oxidize to hematite or goethite over long periods in humid environments.
Care & Maintenance
Clean with a dry cloth or warm soapy water; dry immediately to prevent oxidation (rust). Avoid ultrasonic cleaners and strong acids (HCl will dissolve it). Store away from computerized electronics and other magnets.
Rarity & Value
Common mineral, though well-formed octahedral crystals are sought by collectors. Value is generally low ($5–$50 for standard specimens) unless exhibiting 'Lodestone' (natural permanent magnet) properties or rare crystal habits.
Special Characteristics
Strong ferrimagnetism (will attract a neodymium magnet). Some specimens act as natural magnets (Lodestone). It is one of the most magnetic minerals on Earth.
Lore & History
Historically used as the first compass (Lodestone) by ancient Greek and Chinese sailors. In lore, it is believed to be a 'grounding' stone that aligns the chakras and balances polarities, though these are non-scientific traditional beliefs.