I was just writing out how Silica isn't silicone dioxide aka sand. How good Horsetail tincture can only be made with fresh sapplings where none of the silica has crystalized.
While searching for a recipe I once posted on how to make your own Horestail tincture I ran into the above from Olree and Walters.
****
Silica, Iodine and selenium are heavily yoked together in needed each other to run effectively.
****