Magnetite

Formula: Fe2+Fe3+2O4

Colour: Greyish black or iron black

Lustre: Metallic, Sub-Metallic

Hardness: 5½ – 6½

Specific Gravity: 5.175

Crystal System: Isometric

Member of: Spinel Subgroup > Oxyspinel Group > Spinel Supergroup, Jacobsite-Magnetite Series. Magnesioferrite-Magnetite Series.

Name: Originally called lodestone as early as 1548 and by other names. Named in 1845 by Wilhelm Karl von Haidinger for the locality at Magnesia, Greece (site for lodestone).

As a Commodity: Iron – Magnetite

Magnetite is an important, strongly magnetic iron ore, along with hematite. Nanoinclusions of magnetite crystals cause the iridescence of Rainbow obsidian.