You must have heard of the term Pelotherapy ? If not here is the meaning :
Pelotherapy is the term used for various mud/clay therapies as a beauty and medical treatment. This procedure or therapy has been used since thousands of years and is still prevalent in the society.

The clay helps to replenish important minerals, detoxify body toxins and gives a soothing effect to the skin. They also help in relieving pain of arthritis.

The healing clays or mud are used all round the world in hydrotherapy, natural/alternative medicine, pelotherapy and balneology.

Some of the clays which are commonly used for pelotherapy are:
Bentonite - it has a high PH level and available as sodium bentonite, magnesium bentonite and calcium bentonite. The word bentonite came from word Ford Benton from where it was found.

Montmorillonite - A smectite and french green clay closely related to bentonite in composition and effects.

Illite - A non-swelling clay (mica) with potent healing properties

Some of the uses of Healing Clay are :
External Application :

• Traumatic injury
• Tendonities
• Carpal tunnel syndrome
• Skin conditions like acne, eczema etc
• Bruise, burns etc.
• Chronic headache
• Gall stones

Internally (used under supervision) :

• Mercury poisoning
• liver detoxification
• Food poisoning
• Detoxification of GIT etc.

This article is not much descriptive. You can find wealth of information regarding uses, method of application, indications, contraindications, how to buy etc from internet.