Cobalt-rich, nickel-poor metal (wairauite) in the Ningqiang carbonaceous chondrite

A structurally ordered cubic metal grain containing ~39 wt% Co, 61 wt% Fe, and <0.6 wt% Ni (~Fe₃CO₂) was found associated with troilite and pentlandite in the matrix of the Ningqiang carbonaceous chondrite. This mineral is similar to terrestrial wairauite. Experimental data in the Fe-Co system indicate that this CsCl-type Co-rich metal is stable below 700°C. Phase relations in the Fe-Co-Ni system show that Co cannot fractionate from Ni above 500°C. The dominant opaque minerals of awaruite, magnetite, and pentlandite in Ningqiang sugest relatively oxidizing conditions. -Authors