Greenstone Metabasalt originates from basalt subjected to great heat and pressure over millions of years Naturally green color distinguishes it from unaltered basalts and comes from the presence of various minerals that were formed by these metamorphic forces Excellent source of the valuable plant nutrients calcium, magnesium and iron Can be used for fortifying garden soils with these important mineral elements Ideal for direct application to soils or combining with other natural fertilizers, composts and soil amendments Greenstone Metabasalt originates from basalt subjected to great heat and pressure over millions of years. Its naturally green color distinguishes it from unaltered basalts and comes from the presence of various minerals that were formed by these metamorphic forces. It is an excellent source of the valuable plant nutrients calcium, magnesium and iron and can be used for fortifying garden soils with these important mineral elements. Greenstone is ideal for direct application to soils or combining with other natural fertilizers, composts and soil amendments.