Clay may be a common material found everywhere, but its amazing properties have been helping mankind since ancient times in agriculture and manufacturing. The main groups of clays include Kaolinite (also called Kalaba), Smectite, and Illite. There are approximately 30 different types of “pure clay,” but most “natural clay” deposits are mixtures of different types, along with other weathered minerals. Clay minerals are known as ‘chemical sponges’ as they can hold water and other inorganic ions, which results in holding an unbalanced charge on their surface, due to which some clay minerals are positively charged and some are negatively charged. Due to the presence of water and inorganic ions, c-lay minerals show remarkable characteristics that make them unique for different applications.
Kaolinite
Kaolinite is the most common clay mineral, and entire clay deposits can be composed of this mineral. There are many commercial Kaolinite mines where this mineral is mined in large volumes for its various industrial uses. Kaolinite is named after the Kao-ling, a mountain in Jiangxi Province in China where this mineral was well-known from early times. It is a soft, earthy, usually white, mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of aluminium silicate minerals like feldspar. In many parts of the world, it is coloured pink-orange-red by iron oxide, giving it a distinct rust hue. Lower concentrations yield white, yellow, or light orange colours.
Illite
Illite is considered as a modiied product of muscovite and feldspar formed from weathering and hydrothermal environments; known as a component of sericite. It is commonly found in soil and argillaceous sedimentary rocks as well as in some low grade metamorphic rocks. It is basically a category of non-expanding clay minerals as their chemical composition prevents the entrance of water into the clay structure. They are characteristic of weathering in temperate climates or in high altitudes in the tropics, and typically reach the ocean via rivers and wind transport.
Based on the chemical composition and origin, the clay could have various colours and properties. Some of the most famous ones are: Green clay, Kaolin white clay, Pink clay, Rhassoul Moroccan clay, Brazilian clays, Fuller’s earth, Bentonite clay and Blue clay.
Smectite
This clay mineral is the weathering product of maic silicates, and is stable in arid, semi-arid, or temperate climates. It was formerly known as montmorillonite. Smectite can adsorb large amounts of water, forming a water-tight barrier. It is used extensively in the oil drilling industry, civil and environmental engineering (where it is known as bentonite), and the chemical industry. There are two main varieties of smectite – Sodium Smectite and Calcium Smectite.
- Sodium Smectite is the high-swelling form of smectite, which can adsorb up to 18 layers of water molecules between layers of clay. Sodium smectite is the preferred clay mineral for drilling muds, for creating a protective clay liner for hazardous waste land ills to guard against future groundwater contamination, and for preventing seepage of groundwater into residential basements.
- Calcium Smectite is the low-swelling form of smectite that absorbs less water, and costs less. Calcium smectite is used locally for drilling muds.
Clay Therapy
While the most common use of clay is for making bricks, tiles, and pottery, its medicinal uses are also far and wide. A wide variety of clays are used for medicinal purposes—primarily for external applications, such as clay baths in health spas. This special aspect of clay is known as clay therapy. It is based on the ability of clays and clay minerals to adsorb and retain harmful and toxic substances.
The use of clay in folk medicine goes back to prehistoric times. The first recorded use of medicinal clay goes back to ancient Mesopotamia. Ayurvedic literature recommends its use against a wide range of diseases, from indigestion to conjunctivitis. Many traditional medical texts recommend clean black cotton soil for several skin diseases, including psoriasis and leprosy. Indigenous peoples around the world still use clay widely, which is related to geography. Both Hippocrates and Aristotle, among others, produced classications of medicinal earths.
Clays are frequently used as biomaterials with clinical applications in complementary and alternative medicine as actives and excipients. Though clays have been used as cosmetics by beauticians for a long , the therapeutic values of clay have not yet been recognized by modern science.
The clay fights harmful bacteria such as Escherichia coli and Salmonella typhimurium and even checks the strains of Staphylococcus aureus, which has been increasingly found to be antibiotic-resistant. Lynda Williams, lead researcher of the Arizona State University team, says the antibacterial clay is highly alkaline, with a pH value of 9.4–10, and this property could have made it antibiotic. “We are trying to decipher the chemical properties of the clay and the exact mechanism it uses to kill bacteria,” says microbiologist Shelley Haydel of the Center for Infectious Diseases and Vaccinology at the University of Arizona in the USA.
A study found that osteoarthrosic patients significantly benefited from a 12-day mud-pack application. Calcium bentonite clay, which is found in sub-surface mines in California, has been found to be effective against external injuries. It is also used for the body detoxication.
Many types of skin infections have been healed by the application of medicinal clay. Clay is used in many dermatological over-the-counter remedies, such as acne treatments. In April 2008, the Naval Medical Research Center announced the successful use of a Kaolinite-derived aluminosilicate nanoparticle infusion in traditional gauze known commercially as “QuikClot Combat Gauze.”.
Among the clays commonly used for medicinal purposes are kaolin and the smectite clays, such as bentonite, montmorillonite, and Fuller’s earth.
For external use, the clay may be added to the bath or prepared in wet packs or poultices for application to specific parts of the body. Often, warm packs are prepared; the heat opens up the pores of the skin and helps the interaction of the clay with the body. As always, consult with your primary care physician before embarking on any new health regimen.