Cu – Copper is found in igneous rocks at 55 ppm; shale at 45 ppm; sandstone at 5 ppm; limestone 4 ppm; fresh water at 0.01 ppm; sea water at 0.003 ppm; soils at 2 to 100 ppm (copper is strongly absorbed by humus; there are known areas of the world with extreme copper deficiency); … Continue reading Copper (Cu)