I've seen recipes using kaolin in bath bombs/fizzies.
Here is a description from Mountain Rose Herbs
http://www.mountainroseherbs.com/learn/kaolinclay.html:
Its natural adsorbent properties makes it essential in hygiene products and is often found in soaps, scrubs, poultices, deodorants, facial powders and masks. It is the mildest of all clays and is suitable to add to products created for people with sensitive skin. It helps stimulate circulation to the skin while gently exfoliating and cleansing it. It does not draw oils from the skin, so it can also be used on dry skin types without negative results.
Kaolin Clay is high in calcium, silica, zinc and magnesium, which are beneficial for oily, blemished skin. The clay's mildly drying and disinfectant properties help heal existing blemishes and inflammations, while preventing new ones from forming. It can also be used as a scent fixative.
Here is the bath fizzy that Anne-Marie has on her blog using it.
http://www.soapqueen.com/bath-and-body- ... zzy-fun-2/