Horsetail Grass Tea has high silica content which is vital for human health. Horsetail (Equisetum arvense) is among the oldest of all plants, having dominated the plant world for 100 million years. In ancient times, it was a giant fernlike tree. The twenty species surviving today are miniature versions of their ancestors. Horsetail is known for its abrasive texture. In fact, Horsetail can be used to sand wood or scour and shine metal. This remarkable quality is due to its high silica content. Silica, a vital element of health, is found in all tissues and organs of the body, including the skin, hair, nails, teeth, bones, tendons, and ligaments.