A Horsetail (Equisetum arvense) is a bushy plant that grows in wet areas such as marshes, or beside streams and rivers. It contains naturally occurring Silicon, commonly known as Silica. One of the ways your body uses Silicon is as a component of collagen. Collagen is a protein found in skin and connective tissue (tendons, cartilage and ligaments); and is what gives these tissues their strength and structure.