When listed on a skin care product, magnesium aluminum silicate can have one of two meanings. Most commonly, the term indicates the presence of a white chalk-like powder that occurs naturally in nature in soil clays, but can also be manufactured industrially for use in products. This form of magnesium aluminum silicate is sometimes referred to as white clay, hectorite or kaolin.
The primary benefit of the main form of magnesium aluminum silicate used by the skin care industry is that the ingredient has the ability to retain a large amount of water. This makes magnesium aluminum silicate useful for absorbing excess moisture from liquid skin care formulations to make them less watery or runny. In some cases, magnesium aluminum silicate is added to a liquid, gel, foam or cream to make the product thicker, giving it a more luxurious feeling.
The powdered form of magnesium aluminum silicate can also be added to powdered cosmetics, such as loose powder, eye shadow and blush, to absorb moisture and prevent products from becoming cakey or forming clumps. In liquid foundations and concealers, the chalky texture of magnesium aluminum silicate helps to make the makeup less transparent. By decreasing the transparency, magnesium aluminum silicate allows the makeup to provide fuller coverage to the skin to better hide imperfections of the complexion.
The U.S. Food and Drug Administration (FDA) has approved the powdered or clay form of magnesium aluminum silicate for use in skin care products, listing it as "Generally Regarded as Safe." The skin care products safety review panel known as the CIR Expert Panel has asserted that the powder is safe, but only in limited quantities. This is because the metal aluminum is known to have toxic effects on the nervous system in large doses. Since powdered or clay magnesium aluminum silicate is an additive rather than an active ingredient, it is unlikely to be found in high enough concentrations in skin care products to pose any risk.
The International Journal of Toxicology published a study in 2003 that reported very mild skin irritation in rabbits that were exposed to magnesium aluminum silicate. This suggests that people with very sensitive skin may not be able to use the ingredient due to redness, itching or swelling.
The second type of magnesium aluminum silicate that may be used in skin care and beauty products is a red gemstone that is related to the garnet. Sometimes called pyrope, the gemstone forms when rocks that contain aluminum, magnesium and silicate are exposed to intense heat and pressure over centuries of time. The weathering of this gemstone by water, wind and chemicals in the environment produces the clay and powder that is commonly used in skin care products and goes by the same name.
The magnesium aluminum silicate gemstone has a deep, rich color that is a mixture of burgundy and orange. The gem can be ground and processed for use as a pigment in lipsticks, eye shadows, blushes and skin bronzers. Because of its natural origins, the gemstone is often found in natural skin care collections, where it is chosen over artificial colorants.
Tiny crystals of magnesium aluminum silicate gemstones are included in the formulas of a small number of skin care products, particularly exfoliators and facial scrubs. In these products, the magnesium aluminum silicate fragments create friction, which removes dead skin cells from the surface of the complexion. Exfoliating with magnesium aluminum silicate crystals is meant to mimic microdermabrasion, a professional skin care treatment that uses a tool mounted with diamonds or other gemstones to eliminate old skin cells. The presence of magnesium aluminum silicate in a body scrub or exfoliator can help to resurface the complexion to make fine lines less noticeable and remove discolored and dry skin.
Pyrope is not a toxic substance; however, breathing in the particles of the gemstone can have serious respiratory and neurological consequences. Because the crystals of magnesium aluminum silicate found in skin care products are contained in a cream, liquid or gel, they are unlikely to be accidentally inhaled. People with sensitive skin may experience irritation due to the friction produced by magnesium aluminum silicate scrubs and exfoliators. Typically, this is marked by redness and mild inflammation which typically fade within 24 to 48 hours after use.