Ludwigite

Ludwigite is a magnesium-iron borate mineral: Mg2FeBO5. 
Ludwigite typically occurs in magnesian iron skarn and other high temperature contact metamorphic deposits. It occurs in association with magnetite, forsterite, clinohumite and the borates vonsenite and szaibelyite. It forma a solid solution series with the iron(II)-iron(III) borate mineral vonsenite.
It was first described in 1874 for an occurrence in Ocna de Fier, Banat Mountains, Caraș-Severin County, Romania and named for Ernst Ludwig (1842–1915), an Austrian chemist at the University of Vienna.