Greensand is a mineral mined from natural deposits of glauconite. These deposits are composed primarily of iron-potassium silicate. Greensand is an excellent soil conditioner due to its unique combination of physical and chemical properties which give the gardener the benefits attributed to both sand and clay materials. A great source of potassium and other trace elements. To see more great products like this, check out the rest of our lawn and plant fertilizers.