Doing so resulted in the formations of magnesite, siderite, and numerous varieties of graphite.[9] Other experiments—as well as petrologic observations—support this claim, finding that magnesite is actually the most stable carbonate phase in the majority of the mantle. This is largely a result of its higher melting temperature.[10] Consequently, scientists have concluded that carbonates undergo reduction as they descend into the mantle before being stabilised at depth by low oxygen fugacity environments. Magnesium, iron, and other metallic compounds act as buffers throughout the process.[11] The presence of reduced, elemental forms of carbon like graphite would indicate that carbon compounds are reduced as they descend into the mantle.