6 Photos
Ludwigite
Chemical Formula	Mg2Fe3+BO5
Species	Borates
Crystal System	Orthorhombic
Mohs Scale	5
Specific Gravity	3.6-3.8
Color	Pitch-black, olive-black
Streak	greenish black
Luster	Silky
Refractive Index	n = 1.830 - 1.850 n = 1.830 - 1.850 n = 1.940 - 2.020
Diaphaneity	Opaque
Cleavage	None Observed
Fracture	Fibrous
Crystal Habit：Massive - fibrous commonly in fanlike to felted aggregates
Geological Setting：In contact metamorphic deposits as high-temperature phases.

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.