The Collaborative International Dictionary
Ludwigite \Lud"wig*ite\, n. [Named after the chemist Ludwig.] (Min.) A borate of iron and magnesia, occurring in fibrous masses of a blackish green color.
Wiktionary
n. (context mineralogy English) An orthorhombic-dipyramidal mineral containing boron, iron, magnesium, and oxygen.
Wikipedia
'''Ludwigite ''' is a magnesium- iron borate mineral: MgFeBO.
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, Caras-Severin, Romania and named for Ernst Ludwig (1842–1915), an Austrian chemist at the University of Vienna.