Clays have been used for centuries to beautify and refresh when used as a facial mask.
Cleopatra used clay from the Nile river and the Arabian desert over 1800 years ago, as part of her beauty ritual.
German and Roman spas have been using clay packs and treatments in the spas they built 4,000 years ago. Many of these spas still exist and use clay even today.
Pliney the Elder devoted an entire chapter of his Natural History" to the many uses of clay for pimples, black heads and skin tightening. Many famous naturopaths, such as Kuhn, Just and Kneipp have contributed to the revival of the uses of clay through their natural treatments for arthritus and skin ailgments.
The use of clay with apple cider vinegar can be dated back to the southern French priest of the16th century, Kneipp, and his natural treatments using clay packs and poultices.
Throughout history the use of clay, specifically green clay or bentonite, is well documented. To learn more about clay, look for "Our Earth Our Cure" by Raymond Dexteit, translated by Michel Abehsera in your local health food store or book store.