Diatomaceous Earth Fossil shell flour Our Fossil Shell Flour is Pure Freshwater Diatomaceous Earth. It is of the highest quality available, being greater than 99.5% amorphous silica and less than 1/2% crystalline silica. Fossil Shell Flour Diatomaceous Earth is used for internal and external use. The popularity of Diatomaceous Earth is the result of word-of-mouth testimonials from consumers who are very enthusiastic about the results they have experienced. Diatomaceous Earth has many uses within the garden as well as outside.