Niningerite
Niningerite is a magnesium-rich sulfide found in EH enstatite chondrites, a sign of very oxygen-poor formation.
Niningerite is a sulfide of magnesium with some iron and manganese, (Mg,Fe,Mn)S. It was named after Harvey Harlow Nininger, the American collector and researcher who did much to establish meteoritics as a science in the twentieth century.
The mineral occurs mainly in EH enstatite chondrites. Magnesium normally binds to oxygen in silicates, so finding it bound to sulfur shows that these meteorites formed in an environment extremely short of oxygen. In EL chondrites and aubrites, the equivalent role is taken by alabandite, a manganese-rich sulfide, and the two minerals help tell the enstatite subgroups apart.
The iron and manganese content of niningerite changes with temperature, so it has been used as a rough guide to how hot enstatite chondrites became. Like oldhamite, it can react with moisture, which is why enstatite meteorites need careful dry storage once collected.
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