Terra

Terra is one of the names for the Roman Earth Mother Goddess. The other was Tellus. However, Terra is also a name commonly used to talk about the actual planet Earth (the rock: the crust, the mantle and the core) so it seems an appropriate name for a Goddess which represents that aspect of the Earth, the inorganic aspect. As such, Terra and Gaia can be considered to have a relationship where Terra is Gaia's first home and Gaia represents the Life currently growing on Terra.