The beautiful markings revealed by cutting and chemically
etching these iron meteorites are actually crystals of metal.
They took shape as hot, homogeneous nickel-iron alloy cooled
very slowly. Two different minerals containing different proportions
of iron and nickel crystallized from the molten metal. The
width of the crystals in the geometric patterns called Widmanstätten
structures varies from meteorite to meteorite because of differences
in cooling rate and chemical composition.
The criss-crossing bands in this close-up of Carbo are the
iron-rich alloy kamacite. The triangular areas in between
are the nickel-rich alloy taenite. The image is 80mm across.