Gems and Enchanting Options

[Frostblade10]

First of all, what are black soul gems for? They have the same power and refilability towards weapons.
Second, how does one go about increasing the power of the enchantment i want to make at the mages guild. I want to make an uber fire damage weap but i can only go to 85 (the power of the gem) which is only like 10 fire damage in a small area. Is this connected to a skill?

[Olav]

I haven't started enchanting or soul trapping very much yet, but I think the power depends on the soul you've trapped. A grand/black (yes, I think they're the same) soul gem should be grand soul level to get max out of it (1800 I think, but I'm not sure).

So if you've trapped a rat in a grand soul gem it will have very little enchanting power. I'm not sure what creatures give max power in Oblivion. Golden Saints and Ascended Sleepers(?) gave max power in Morrowind, but I don't think they're in Oblivion. Anyone?

And I'm not sure if the skill level is relevant, but probably, although there is no longer enchantment skill in Oblivion like in Morrowind.