A method for purifying diatomaceous earth, whose natural colloidal structure is retained, which includes preparing a suspension of diatomaceous earth in a liquid wherein diatomaceous earth is insoluble, separating diatomaceous earth from the suspension, treating diatomaceous earth with an inorganic or organic acid, heat-treating the thus obtained product at a temperature not higher than 300° C., subjecting the product obtained to oxidative treatment and drying the purified product.
