Chassigny is an olivine cumulate rock (dunite).

It consists almost entirely of olivine with intercumulus pyroxene, feldspar, and oxides.

It was the only known chassignite until NWA2737 was found in the Moroccan Sahara in northwest Africa.

[4] Chassigny is particularly important because, unlike most SNCs, its noble gas composition differs from that in the current Martian atmosphere.

These differences are presumably due to its cumulate (mantle-derived) nature.