According to Mountain Rose Herbs:
“Bentonite, also referred to as Montmorillonite, is one of the most effective and powerful healing clays. Bentonite can be used externally as a clay poultice, mud pack or in the bath and, in skin care recipes. A good quality Bentonite should be a grey/cream color and anything bordering “pure white” is suspect. It has a very fine, velveteen feel and is odorless and non-staining. The type of bentonite offered by Mountain Rose herbs is a Sodium Bentonite.”
Bentonite Clay is composed of aged volcanic ash. The name comes from the largest known deposit of Bentonite Clay located in Fort Benton, Wyoming.