Historical uses: A wonderful natural source of calcium and silica in a glycerine based extract. The silica in horsetail grass converts to calcium, and the other herbs work in close conjunction with this master calcium herb. Calcium is need for nerve sheath, vein and artery walls, bone, teeth, etc. This combination is all pure herbs. It is also used for cramps, "charlie horses," and for all calcium needs in the body. Calcium formula: Horsetail Grass, Oat Straw, Nettle and Valerian.