mineral

Magnetite

Magnetite (Fe3O4)

Hardness: 5.5-6.5 on Mohs scale; Color: Black to dark gray; Luster: Metallic to submetallic; Crystal Structure: Isometric; Cleavage: None/Indistinct; Specific Gravity: 5.1-5.2; Streak: Black. It is naturally ferrimagnetic.

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

Identified June 3, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous, metamorphic, and sedimentary environments. Often found as an accessory mineral in igneous rocks like granite and basalt, or in banded iron formations (BIFs). This smooth, rounded specimen (pebble) suggests water-worn erosion in a river or marine environment.

Uses & applications

Primary ore of iron; used in manufacturing steel, heavy media separation, water filtration, and as a pigment. High-quality specimens are collected for their magnetic properties.

Geological facts

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

Field identification & locations

Identify in the field using a strong magnet (it will be strongly attracted) and checking for a black streak on a porcelain plate. Commonly found in heavy mineral sands or as small grains in dark igneous rocks.