Aubrite
A pale achondrite made almost entirely of iron-free enstatite pyroxene, formed under very oxygen-poor conditions.
Aubrites are the white sheep of the meteorite world. They are achondrites (meteorites that melted on their parent body) built mostly from enstatite, a magnesium pyroxene that contains almost no iron oxide. Without iron to tint it, the enstatite is white or nearly colourless, so freshly broken aubrites look more like a lump of marble or chalky granite than a dark space rock.
They formed in an extremely oxygen-poor setting, the same chemical world as the enstatite chondrites. That is why they hold unusual minerals such as oldhamite (calcium sulfide) and grains of metal with traces of silicon. The group is named after Aubres in France, which fell in 1836. The best-known aubrite is Norton County, which fell on the Kansas–Nebraska border in 1948; its main mass, at roughly a tonne, is one of the largest achondrite stones ever recovered.
To recognise an aubrite, look for a very pale, often brecciated interior of large white crystals, sometimes with darker fragments. The fusion crust can be thin and glassy, even light brown, rather than the usual black. Their parent body is uncertain, though some bright E-type asteroids have been suggested.
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