mineral

Magnetite / Ironstone Pebble

Magnetite (Fe3O4)

Hardness: 5.5-6.5; Color: Black to dark gray; Luster: Metallic to submetallic; Crystal Structure: Isometric (often rounded as a stream pebble); Specific Gravity: 5.1-5.2

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

Identified July 1, 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 (often rounded as a stream pebble); Specific Gravity: 5.1-5.2

Formation & geological history

Forms in igneous, metamorphic, and sedimentary environments. Often found as heavy mineral sand or stream-worn nuggets concentrated by water action (placer deposits).

Uses & applications

Primary ore of iron; used in heavy media separation, as a pigment, and as a magnetic mineral for educational or industrial purposes.

Geological facts

Magnetite is the most magnetic of all the naturally-occurring minerals on Earth. Some specimens, known as lodestones, act as natural magnets and were the first compasses used in history.

Field identification & locations

Identify using a magnet; it should be strongly attracted to one. It often leaves a black streak on a porcelain plate and feels significantly heavier than a normal stone of the same size.