"Sparkly" = "tending to sparkle", and "sparkle" = "to issue in or as if in little sparks, as fire or light". So I would have thought sparkly has a lot to do with light.No. It covers stuff with sparkly dust which blinds them. Nothing there has anything to do with light.
What happens if the target is standing with his/her back to the wall, and their is a fresco or mosaic on the wall. Can you read it?I'd visualize it glowing with a bright but very self contained light. So if you cast it in complete darkness, you pretty much see a bunch of gold dots on a black shadow. You wouldn't see anything else in the area
The spell says "A cloud of golden particles covers everyone and everything in the area . . . visibly outlining invisible things for the duration of the spell. All within the area are covered by the dust, which cannot be removed and continues to sparkle until it fades."The spell does not provide any illumination, unless you count outlining the target as "illuminating" it.
Given that faerie fire, which does outline things in a glow, has the [light] descriptor, I would infer that Glitterdust does not create glowing particles, and that the dust only sparkles when light falls on it (and so is reflective rather than itself illuminating). That's different from TwoSix's interpretation. I think I'm agreeiing with [MENTION=7706]SkidAce[/MENTION] and [MENTION=7808]Deset Gled[/MENTION].