mineral

Magnetite Nodule

Magnetite (Fe3O4)

Hardness: 5.5-6.5; Color: Black to dark grayish-black; Luster: Metallic to sub-metallic; Crystal structure: Isometric (often octahedral); Streak: Black; Specific Gravity: 5.1-5.2

Hardness: 5
Color: Black to dark grayish-black
Luster: Metallic to sub-metallic

Identified July 10, 2026More mineral →

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Physical properties

Hardness: 5.5-6.5; Color: Black to dark grayish-black; Luster: Metallic to sub-metallic; Crystal structure: Isometric (often octahedral); Streak: Black; Specific Gravity: 5.1-5.2

Formation & geological history

Formed in igneous rocks like basalt or gabbro, metamorphic rocks, and as a heavy mineral in sedimentary beach or river sands. This specific specimen appears to be a rounded nodule or a worn crystal aggregate.

Uses & applications

The most important ore of iron; used in the manufacture of steel, as a pigment (mars black), as an abrasive, and in magnetic separation processes.

Geological facts

Magnetite is the most magnetic of all the naturally-occurring minerals on Earth. Naturally magnetized pieces called lodestones were used by early navigators as the first compasses.

Field identification & locations

The defining field identification test is its strong attraction to a magnet. Look for its heavy weight (high specific gravity) and black streak on a porcelain plate. Common in heavy sand deposits.