Guaranteed Potency 10% Vegetal Silica From Springtime Horsetail An Herbal Supplement World Organic Silica 500 contains the highest potency of actual Silica of any leading brand. Our special formulation combines the whole herb with all of the naturally occurring flavones found in springtime horsetail herb, as well an extra high potency extract to provide a balanced source of vegetal Silica. In the human body, silica is found in the hair, nails, and bones.