mineral

Magnetite

Magnetite (Fe3O4)

Hardness: 5.5-6.5; Color: Black, iron-black, or dark gray; Luster: Metallic to submetallic; Crystal Structure: Isometric (octahedral); Cleavage: None (parting sometimes present); Specific Gravity: 5.1-5.2

Hardness: 5
Color: Black, iron-black, or dark gray
Luster: Metallic to submetallic

Identified February 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed in high-temperature igneous environments (magmatic segregation) and metamorphic rocks. This specimen is a water-worn river cobble showing rounded edges from mechanical erosion.

Uses & applications

Primary ore of iron; used in heavy media separation, as a toner in photocopiers, and in industrial pigments. Naturally magnetic varieties (lodestone) are popular specimens for collectors.

Geological facts

Magnetite is the most magnetic of all the naturally-occurring minerals on Earth. It was used by ancient navigators who observed that suspended lodestones pointed towards the magnetic poles.

Field identification & locations

Identify in the field using a strong magnet (it will strongly attract the magnet) and a black streak on a porcelain plate. Found globally in iron-rich geological regions.