Mineral Species: Magnesioferrite

Chemical Formula: Mg(Fe3+)2O4

Chemical Name: Magnesium Iron Oxide

Mineral Class: Oxides

Mineral Notes: Magnesioferrite most commonly forms near fumaroles. Also in high-grade (sanidinite facies) combustion-metamorphosed marls and in metamorphosed dolostones. An accessory mineral in some kimberlites, carbonatites, and alkali gabbros. Finally, as skeletal inclusions in glassy spherules in sediments attributed to bolide impact debris. It belongs to the Spinel Group and forms a series with Magnetite. It is named after the content of magnesium and FERRIC iron.

Description: Small grains and crystals of black Magnesioferrite. Under magnification some have rounded sides, almost like little spheres. There is gradation in size through the specimen. The largest crystals occur near the base matrix, becoming increasingly smaller towards the edge. Very strong metallic apperance and luster.

Location: Langban, Wermland, Sweden.