mineral

Magnetite / Ironstone

Iron(II,III) oxide (Fe3O4)

Hardness: 5.5-6.5; Color: Black, dark gray with brownish tint; Luster: Metallic to sub-metallic; Crystal structure: Isometric/Octahedral; Cleavage: None (parting); Specific gravity: 5.1-5.2

Hardness: 5
Color: Black, dark gray with brownish tint
Luster: Metallic to sub-metallic

Identified June 20, 2026More mineral →

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Physical properties

Hardness: 5.5-6.5; Color: Black, dark gray with brownish tint; Luster: Metallic to sub-metallic; Crystal structure: Isometric/Octahedral; Cleavage: None (parting); Specific gravity: 5.1-5.2

Formation & geological history

Formed in igneous, metamorphic, and sedimentary environments. Often found in Banded Iron Formations (BIF) or as an accessory mineral in igneous rocks like basalt. Some specimens date back billions of years.

Uses & applications

Primary ore of iron; used in heavy media separation, steel production, water filtration, and occasionally as an industrial abrasive. Polished specimens are used in jewelry and by collectors.

Geological facts

Magnetite is the most magnetic of all the naturally-occurring minerals on Earth. Naturally magnetized pieces called lodestones were used to create the first compasses in history.

Field identification & locations

Identify by its black streak, high density (heavy for its size), and strong attraction to magnets. It is commonly found in beach sands (as black sand), mountain ranges, and near iron mines.