In the Infestation universe, any fusions involving Barites are permanent. This is because of the properties of Barites. They don't necessarily feed off of other gems, but they 'infect' them so to speak. (This is an infestation au what did you expect me to say?) This makes any gem that fuses with them become a Barite as well. Since the Barite 'virus' is growing on top of as well as within the second gem, it forms a strong bond between them that keeps them from unfusing, no matter how panicked or adverse to each other they become. Since fusing with other kinds of gems is forbidden in Homeworld, these fusions have no choice but to turn against it--though not necessarily becoming Crystal Gems. Essentially, fuse with a Barite and man you're on your own.