Mundrabilla is a riddle. When the metal was molten, the graphite and sulfide inclusions should have separated from it--like oil from water. Instead, they are thoroughly mixed, and no one is certain why.
Nakhla formed on Mars when dense pyroxene (greenish-gray) and olivine (brown) crystals settled out of molten rock. It contains water-bearing minerals, supporting the idea that the Martian valleys once carried water.