Calcium Aluminum Borosilicate

Calcium Aluminum Borosilicate is an inert mineral/synthetic mica-like glass used in cosmetics as a pigment/pearlizing filler, typically present at low-to-moderate percentages in color products and considered non-reactive with minimal skin penetration. Clinical irritation potential is generally low, but fine particulate minerals can cause mild mechanical irritation or dryness on compromised barriers (e.g., eczema, post-procedure) and may irritate periocular skin in some users, so I do not score it as fully inert for highly sensitive populations. Safety Notes: Calcium Aluminum Borosilicate is used as an effect pigment/extender (often in pearlescent/mica-like composites) and appears at trace-to-low levels (~0.01–0.5%) in skincare where it’s included mainly for subtle optical blur or glow (e.g., primers, tinted moisturizers, illuminating lotions, some sunscreens). In high-impact consumer color cosmetics that are still OTC (highlighters, shimmer powders, eye shadows, luminous pressed/loose powders), it can be a major component of the powder phase and is commonly seen in the 5–25% band, with some effect-pigment–heavy formulas reaching ~30–35%. Rinse-off products rarely use it, and when they do (shimmer body washes/soaps) it is typically kept low for suspension and rinse-off aesthetics.