mineral

Magnetite

Magnetite (Fe3O4)

Hardness: 5.5-6.5; Color: Black to dark gray; Luster: Metallic to submetallic; Crystal Structure: Isometric/Octahedral; Cleavage: None (parting sometimes visible); Specific Gravity: 5.1-5.2

Hardness: 5
Color: Black to dark gray
Luster: Metallic to submetallic

Identified June 18, 2026More mineral →

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Physical properties

Hardness: 5.5-6.5; Color: Black to dark gray; Luster: Metallic to submetallic; Crystal Structure: Isometric/Octahedral; Cleavage: None (parting sometimes visible); Specific Gravity: 5.1-5.2

Formation & geological history

Typically forms as an accessory mineral in igneous rocks like basalt or granite, but also found in metamorphic rocks (schist, gneiss) and sedimentary black sands. Often concentrated via hydrothermal activity or contact metamorphism.

Uses & applications

Primary ore of iron; used in manufacturing steel, heavy media separation, water treatment, and as magnets; occasionally used as jewelry stones called lodestones.

Geological facts

Magnetite is the most magnetic of all naturally occurring minerals on Earth. Some varieties, known as lodestones, act as natural magnets and were used by ancient mariners to create early compasses.

Field identification & locations

The most effective field identification is its strong attraction to magnets. It can be identified by its black streak on a porcelain plate and its high density (heavy feel for its size). Commonly found in riverbeds as black sand.