A closer look at this shiny polish ingredient.
What it is: A transparent mineral that is mined from the earth usually in thin sheets; Muscovite is the most common mica mineral. It is also called white mica.
Where it comes from: Mica is mined all over the world. In the U.S., scrap and flake mica comes from Arizona, New Mexico, South Dakota, Georgia, North Carolina, and South Carolina. Canada, India, Finland, and Japan all export flake mica to the U.S.
Properties: Mica crystals are six-sided. They are relatively light, soft, and flexible. The best way to tell a mica is by the thin, transparent sheets that it splits into. Mineralogists call micas sheet silicates because their molecules combine to form distinct layers. They are often found in igneous rocks such as granite and metamorphic rocks such as schist. Mica layers are what make some rocks sparkle. Although mica is often thought to have its own particular color, the different colors of micas are produced by the optical reflection of their multiple layers. The theory behind the colors of mica is the same as that of rainbows or soap bubbles (neither the rainbows nor soap bubbles have their own color). We see the different colors through the light interference of the mica base and the thin film of titanium dioxide coating the base.
What it’s good for: Mica is a common ingredient in nail polish, helping give it a lustrous sheen. Even though mica is naturally occurring, mica as found in nail polish is classified as toxic and also as a bioaccumulator (meaning it tends to accumulate in the bodies of animals, including humans). Nevertheless, mica is at present classified as a low risk nail polish ingredient. According to CND’s chief scientific advisor Doug Schoon, “Mica is very safe to use in cosmetics.”
Where you’ll find it: Nail polish, mineral cosmetics
Other uses:It is also used in electronic insulators (Mica is heat-resistant and does not conduct electricity.), paint (as a pigment extender and a suspension agent), in the well-drilling industry (as an additive to drilling “muds”), as well as the plastics and rubber industries as a filler. Colonial Americans used the thin sheets of large mica crystals as glass for windows.