AbstractThis paper describes Miconite (hydrated potassium, magnesium aluminosilicate) and explains the processability and properties of Miconite‐filled propylene homopolymer. With particles averaging 2.5 and 44 microns, this study found the compound processability, as given by its melt index, unchanged for filler loadings lower than 35%. Tensile strength of the original polymer doubled with the addition of the first 10% of Miconite and stayed constant for all loadings tested up to 60%. Tensile modulus increased linearly with filler loading. Elongation and impact behavior showed negligible decreases for loadings lower than 30%. Deterioration by ultraviolet and/or heat‐aging was negative. Miconite provides matrix materials with fire and smoke retarding qualit