Snow White mica from Mad Micas contains titanium dioxide.
From the Snow White Mica page: Ingredients: Fluorphlogopite (CAS 12003-38-2), titanium dioxide (77891)
Nurture Soaps list exactly the same ingredients for their Winter White Mica too.
I use titanium dioxide at a rate of 1 teaspoon per pound of oils and have had zero issues with it.
The recommended amount for the Winter White Mica is 3 teaspoons per pound.
Regarding Fluorphlogopite:
Synthetic Fluorphlogopite (also spelled Fluorophlogopite) is a fluorine substituted mineral composed of magnesium aluminum silicate sheets, weakly bound together by potassium. Synthetic Fluorphlogopite is used in a wide range of cosmetics and personal care products including bath products, eye makeup, lipstick, face makeup, as well as nail and skin care products.
I think I'll stick with good ol' titanium dioxide for whitening my soaps. Less expensive too. Four ounces of Winter White is $14.30, four ounces of TD is $6 or so.
Not hatin'... just sayin'.