All Natural Fertilizer Espoma Greensand is the highest quality, all natural, non-burning, purest Greensand obtainable. Espoma Greensand is mined from natural deposits of glauconite. These deposits are of marine origin and are composed primarily of iron–potassium silicate, which gives it it’s bluish green color. Potassium is an essential nutrient needed by all plant life. Other valuable properties of Espoma Greensand are it’s ability to loosen clay soils, bind sandy soils, and increase the water holding capacity of all soils. It is an exceptional soil conditioner for flower beds, gardens and lawns.