@Don:
Mhh yeah, pretty cool thoughs but actually they`re proved wrong. In movie 4 a guy named Gasparde appeared who had the ame-ame no mie, which was a logia-DF. So even when made by a living creature, Candy was a Logia-DF.
No, you need to throw that logic right out the window. The anime and movies are not canon, and you should NEVER take them as such. "Oda would have told them" is not an argument; case in point, Laboon the iceburg. Some things go through Oda, sure, or Oda might expressly tell them to make sure they do this or that, but expecting every decision to go through Oda is ridiculous, and clearly not what happens.
@Don:
I guess when Oda had such a rule like Ubiq pointed it out, he would have said that ame-ame no mie should be handled like a paramecia.
Banking off what I just said above, it's true Oda never explicitly outlined what a logia can and cannot be, but he gave us a pretty good rule of thumb, and thus far the canon fruits have fit Oda's own description (that Ubiq expands on):
Volume 35 SBS: Logia (nature) type can turn their bodies into something completely different. Zoan (animal) type can turn into animals. Everything aside from those is lumped into the Paramecia (superhuman) category.
Volume 58 SBS: Whitebeard has the Gura Gura Fruit. It's easy to think that he is an "Earthquake Human" and must be Logia, but if that was so, he'd have to become an earthquake himself. Whitebeard creates earthquakes, in other words he's a "Vibration Human". That means he's a Paramecia who isn't any weaker than the Logias. Note: gura gura is the onomotopoeia for shaking things, and doesn't mean earthquake. Note that Oda admits that an earthquake fruit, being a natural phenomena, would be a logia, while a vibration fruit, being something created, would be paramecia.