Disclosed is a particulate composition comprising at least 10 % by weight oligodynamic silver- coated sand particles, said oligodynamic sand particles having diameter in the range of 50 to 10,000 µm and being composed of etched sand particles carrying elemental silver deposit, wherein the oligodynamic sand particles have a total silver content of 10 to 5,000 mg/kg and wherein not more than 30 % by weight of the silver contained in the oligodynamic sand particles is present in the form of nanoparticles having diameter of 100 nm or more. The treated sand particles deliver a silver ion leach of desired value in the range of 50 to 200 ppb by weight. The oligodynamic silver coated sand particles of the present invention exhibit prolonged, constant anti-microbial activity and do not suffer from uncontrolled leaching.
