Oven cleaner –
Ordinary combination stones – I have taken oil out by sharpening a time or two using oven cleaner (gloves) and subsequent sharpenings lubed with Dawn – because old ‘oil-stones’ will continue having oil come to the surface. Jap water stones might dissolve in oven cleaner, haven’t had the pleasure of buying one that had seen oil, so don’t know, yet.
Hard natural stones like washita, hard black, transluscent white, also will lend selves to said.