Wiktionary
niningerite
n. (context mineralogy English) A magnesium-iron-manganese sulfide mineral.
Wikipedia
Niningerite
Niningerite is a magnesium- iron- manganese sulfide mineral with the chemical formula MgS that is found in enstatite chondrite meteorites. Niningerite is the magnesium-dominant analog of keilite. This mineral is named after Harvey H. Nininger.