Both spellings are prevalent; the original language did not have a j so it was spelt with an i (the same is the case with, for example, the name Jesus; in the original it was something like Iesos). The j spelling in many such words is the anglicised version, I believe.
CAT-holics 
Is it “Alea Jacta Est” or “Alea Iacta Est”??
Both spellings are prevalent; the original language did not have a j so it was spelt with an i (the same is the case with, for example, the name Jesus; in the original it was something like Iesos). The j spelling in many such words is the anglicised version, I believe.
regards
J (or maybe I?)