Magnesium aluminum silicate (MAS) is a refined mineral compound derived from natural clay deposits, serving as a versatile ingredient across numerous consumer and industrial products. Its primary roles are to act as a thickening and suspending agent, changing the texture and stability of liquid formulations. This mineral is instrumental in ensuring that complex mixtures, like cosmetics and pharmaceuticals, maintain a uniform and consistent quality over time.
Chemical Composition and Natural Source
Magnesium aluminum silicate is a hydrated silicate mineral, meaning its chemical structure incorporates water molecules alongside magnesium, aluminum, and silicon oxides. It is a member of the smectite group of clay minerals, which are characterized by their layered structure. The specific composition can vary slightly, but the core components of magnesium, aluminum, and silicon remain consistent.
This compound originates from naturally occurring silicate ores, such as those rich in montmorillonite clay. The raw material is mined from the earth and then subjected to an extensive purification process to remove impurities and contaminants. This refining ensures the final product is suitable for pharmaceutical and cosmetic use, resulting in an off-white, odorless powder.
How Magnesium Aluminum Silicate Functions
The unique function of MAS stems from its colloidal structure when dispersed in water. The mineral consists of microscopic platelets that have a negative charge on their faces and a slightly positive charge on their edges. When hydrated, these platelets interact, with the positive edges of one platelet attracting the negative face of another, building a three-dimensional “house of cards” network.
MAS acts as an effective suspending agent by physically trapping insoluble particles, like pigments in makeup or active drug ingredients in a liquid medication, preventing them from settling to the bottom. This ensures the product remains homogenous and the active components are evenly distributed, which is crucial for consistent dosing and product performance.
MAS exhibits thixotropy, meaning it is thick when at rest but becomes fluid when shaken or stressed. When a product containing MAS is still, the “house of cards” structure maintains a high viscosity, keeping everything suspended. When external force is applied, the structure temporarily collapses, and the product thins out for easy pouring or spreading, quickly reforming once the stress is removed.
Primary Uses in Pharmaceuticals and Cosmetics
Magnesium aluminum silicate is a workhorse ingredient in the pharmaceutical industry, primarily in liquid dosage forms. Its suspending capabilities are used to stabilize oral suspensions, such as antacids or liquid antibiotics, where the active drug particles must remain evenly dispersed for accurate dosing. The thixotropic nature ensures the medication is easy to pour, but the drug does not settle into a hard, non-redispersible sediment at the bottom of the bottle.
In solid pharmaceuticals, MAS can serve as a binder to hold the components of a tablet together or as a disintegrant to help the tablet break apart quickly once ingested. The compound’s function as an adsorbent is also utilized, helping to manage moisture or bind to certain substances within the formulation. The maximum dosage in some oral preparations can reach as high as 60% of the formulation.
In products like foundations, mascaras, and topical creams, MAS prevents the separation of oil and water components and keeps colored pigments from settling. It also modifies the texture, giving products a desirable, smooth feel and improving spreadability upon application. For oily skin formulations, MAS offers an additional benefit as an absorbent, helping to mattify the skin by soaking up excess oil and sebum.
Safety and Regulatory Status
Magnesium aluminum silicate is widely regarded as safe for use in the concentrations typically found in consumer products. Regulatory bodies have reviewed the ingredient, and it is commonly approved for use in both pharmaceutical and cosmetic applications. Because it is an inert mineral, it is not absorbed through the skin or the digestive tract, meaning it poses minimal systemic risk.
It is considered safe in cosmetics when formulated to be non-irritating, and concentrations up to 30% have been reviewed without safety concerns. The main precaution involves the inhalation of the raw powder during manufacturing, which is a common concern for any finely powdered substance.