I agree. But I suppose my post could be misconstrued to where people would think that’s what I was implying.
Uh… So what if an icicle were iridescent?
Then I guess that means that the katana would need to be transparent like the icicle in order to “glow”. Regardless of Iridescent texture mapping/masking, or however the effect works. I know. It’s 2 separate things.
“Glow” I’m going to assume the icicle item refracts nearby light to give the glowing effect. The icicle itself is not the source of the “glowing” - just the nearby light sources.
Eh, so anyway… You’d have the cool glowing effect, but with the rainbow’y iridescent color. 
But if I’m still wrong about whatever then never mind. My fault for not being more specific.