Rock Identifier
Magnetite (Lodestone variety) (Magnetite (Iron(II,III) oxide, Fe3O4)) — mineral
mineral

Magnetite (Lodestone variety)

Magnetite (Iron(II,III) oxide, Fe3O4)

Hardness: 5.5-6.5; Color: Iron-black to dark grey; Luster: Metallic to submetallic; Crystal Structure: Isometric (often octohedral); Cleavage: None (parting sometimes visible); Specific Gravity: 5.1-5.2 (very heavy for its size)

Hardness
5
Color
Iron-black to dark grey
Luster
Metallic to submetallic
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Physical properties

Hardness: 5.5-6.5; Color: Iron-black to dark grey; Luster: Metallic to submetallic; Crystal Structure: Isometric (often octohedral); Cleavage: None (parting sometimes visible); Specific Gravity: 5.1-5.2 (very heavy for its size)

Formation & geological history

Forms in igneous rocks like basalt or gabbro, metamorphic rocks, and as heavy mineral sand in sedimentary environments. Magnetite is one of the most common oxide minerals and occurs in geologic ages ranging from the Archean to the present.

Uses & applications

Primary ore of iron; used in iron and steel manufacturing; industrial applications include heavy media separation and toner for laser printers; also used in magnets and occasionally as a collector's mineral.

Geological facts

Magnetite is the most magnetic naturally occurring mineral on Earth. Natural magnets, known as lodestones, were used by ancient mariners as the very first compasses. It is also found in the brains of some animals (like pigeons) to help with navigation.

Field identification & locations

Identify in the field by its high density (feels heavy), black streak tests, and most reliably, its strong attraction to magnets. Found globally, especially in Sweden, USA (New Jersey, New York), South Africa, and Russia. Small water-worn pebbles like this are common in riverbeds or beach 'black sands'.

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