Can an elementalist fire mage cast geyser?

[Ravingdork]

It appears to be both on their specialist and prohibited list. So which one wins out?

This commonality appears to be true of other spells as well.

[Abyssian]

As weird as it may seem, both Fire Wizards and Water Wizards not only can cast it, but can actually cast it as a "specialty" spell, both as a 5th level spell.

[Artanthos]

A lot of spells common to all elementalist lists.

[Zemier]

Would the same be true for any spell that used fire and water?