July 1, 2013
Used in everything from pencils to deodorants, this is a versatile mineral. What the heck is it?
By Bill Langer
This article is about an industrial mineral that is a rare, greasy, white type of magnesium-lithium clay. It consists of extremely small, flake-shaped crystals and is formed by the alteration of volcanic ash and tuff by hydrothermal waters. This specialty clay has an unusual ability to form strong gels in water at low concentrations of clay; thus it has many, many applications. It is used in paint to stop sags and drips. Adding this clay to adhesive allows the adhesive to stay on top of paper rather than soaking into paper. The graphite compound in pencil lead is bound by this clay. It is used as a gelling agent when drilling oil and gas wells. The cosmetics industry uses the clay in the formulation of lipstick, face makeup, eye shadows, rouge, mascara, skin gels, skin creams, skin lotions, and hair care products. It is also an excellent clarifier of beverages. Some of this clay is processed for its lithium content, which is used in pharmaceuticals, fireworks (red color), batteries, and numerous other applications.
If you know what the heck I am talking about, raise your hand.
Gross! The person next to you has dingy yellow stains under their armpits. This special clay could have prevented that embarrassing situation. Let me explain.
Contrary to popular belief, sweat by itself does not cause those yellow stains. Armpit-ologists tell us that our sweat glands are constantly producing sweat that travels through a sweat duct out onto the surface of our skin. When we are exposed to heat, physical exertion, stress, or nervousness, our sweat glands produce a lot more sweat.
Some folks try to limit sweat through the application of solid antiperspirants, all of which include an aluminum-based compound as their main active ingredient. The aluminum salts are soluble as long as they are in the antiperspirant. When they are applied to skin and come in contact with sweat, the pH rises causing the aluminum salts to precipitate out and form a plug over the sweat glands. Sweat continues to be produced by the sweat gland but the plug keeps the sweat from reaching the surface of the skin. The plugs are shallow enough that they come out when showering. Unfortunately, the plugs also come out when there is too much perspiration, and the sweat and deodorant are washed onto the clothing.
The mixture of deodorant and sweat, according to some experts, is the cause of yellow armpit stains. Can you believe that? The very substance that keeps your pits nice and dry may also be wreaking havoc on your shirts. Recognizing that their product may be contributing to yellow stains, antiperspirant companies have spent beaucoup dollars figuring out how to provide wetness protection and prevent yellow stains from forming.
As you might have guessed, the clay I am talking about is used in some antiperspirants. It helps keep stick antiperspirants from crumbing, smoothes the application, controls the payout rate, and provides a soft skin feel. It is also used in some roll-on and spray antiperspirants to keep the aluminum salts in suspension.
But what really has caught the attention of the cosmetics industry is that the iron content of this particular type of clay is much lower than most other clays. Some studies show that replacing other clays in antiperspirant with this specialty clay reduces the staining potential.
What the heck am I talking about?
Now put your arms down.
Bill Langer is a consulting research geologist who spent 41 years with the U.S. Geological Survey before starting his own business.
He can be reached at