"with Displacement, Black is zero and White is High.. whats the scale in Specular? is black untouched or transperent and White is mirror finish?"

Black = 0 = no specularity. White  = 1 = full specularity. Grey-scales are in between. Transparency is not involved....

Specularity takes the light directed at  the surface, and uses that to decide how much of the surface should be "brightened" (by adding the the specularity colour, not the lights themselves).

Plugging a node into the specularity value (not the colour) will alter the amount of the effect.

I think. I'd be quite happy to be proven wrong:-)) But I think I'm right...

Cheers,
Diolma