mineral

Black Sand (Magnetite Sand)

Magnetite (Fe3O4)

Hardness: 5.5-6.5; Color: Black to dark gray; Luster: Metallic to submetallic; Crystal Structure: Isometric; Specific Gravity: Approx. 5.17; strongly magnetic.

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

Identified April 29, 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; Specific Gravity: Approx. 5.17; strongly magnetic.

Formation & geological history

Formed by the weathering of igneous or metamorphic rocks containing iron-bearing minerals. The heavy minerals are concentrated by water action (placer deposits) on beaches or riverbeds.

Uses & applications

Used as a major ore of iron, in heavy media separation, as a pigment, and occasionally as a specimen for educational or decorative sand art.

Geological facts

Magnetite is one of the most magnetic natural minerals on Earth. It was used by ancient sailors as a primitive compass because it would align with the Earth's magnetic poles.

Field identification & locations

Can be identified in the field using a simple hand magnet; the sand grains will readily cling to the magnet. Commonly found on beaches near volcanic activity or in heavy mineral patches on riverbanks.