Masterwork + special magic quality

[Stokkem]

I see that a masterwork weapon gives it the +1 enhancement bonus needed to add a special quality, yet I see threads saying you need the +1 magic enhancement bonus.

I suppose there is some rule I've missed that specifies this, and I was wondering if anyone could tell me with reference to RAW how this works. I am asking because our group had a disagreeance, and we are interested in what the rules specifically allows or disallows.

In other words: Where is the rule saying the enhancement bonus on a mwk weapon does not qualify for the special magic qualities.

Thanks in advance!

[Orfamay Quest]

The rule source is in the magic weapons section: "A weapon with a special ability must also have at least a +1 enhancement bonus. Weapons cannot possess the same special ability more than once."

The masterwork bonus doesn't qualify because it's not an (unlimited) +1 enhancement bonus; it's a +1 enhancement bonus to hit, but not to damage.