Like the title says. I don't see a trait on the pearly white spindle or anything in the description that explicitly says it does its healing by means of positive energy/vitality. However, the fact that the resonant power explicitly grants resistance 1 to negative damage might imply that. Seems RAW that the healing is not of a specific type, perhaps more akin to "soothe" than "heal", so it should work on a skeleton.
No official ruling that I know of, but the healing the stone does hasn't got the Vitality/Positive trait, so it's fair game for skeleton PCs to use as far as I can tell. The point of Void resist is just wasted on your character, is all.
