Magnetite

Physical Properties

Hardness: 5.5-6.5 on Mohs scale; Color: Black to silvery gray; Luster: Metallic to sub-metallic; Crystal structure: Octahedral; Cleavage: None (has subconchoidal fracture); Specific gravity: 5.1-5.2

Formation & Geological History

Forms in igneous, metamorphic, and sedimentary environments. It is often found in igneous rocks as a primary accessory mineral and can also form via hydrothermal replacement. Large deposits are often found in Precambrian banded iron formations.

Uses & Applications

Primary ore of iron; used in heavy media separation, as a pigment in paints, and in magnetic storage media. High-quality specimens are popular for mineral collecting.

Geological Facts

Magnetite is the most magnetic naturally occurring mineral on Earth. Naturally magnetized pieces of magnetite are called lodestones and were used as the first primitive compasses.

Field Identification & Locations

Identify in the field using a strong magnet (it will be strongly attracted) and its black streak on a porcelain plate. Commonly found in heavy sand deposits on beaches or in igneous rock outcrops.

Identified on: 5/10/2026

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