Horsetail is very rich in the mineral ingredient silica/silicon, which strengthens hair strands, as well as nails and bones!  The mineral silica found in a horsetail supplement for hair growth doesn’t just help the fragility of the hair; as an added bonus it also improves its sheen, elasticity and texture. Horsetail also contains selenium, a mineral that is essential for the proper growth of your hair, as it helps your body process iodine, which regulates hair growth as well.