 With the average concentration of about 8 parts per million ( ppm ) , samarium is the 40th most abundant element in the Earth 's crust . It is the fifth most abundant lanthanide and is more common than elements such as tin . Samarium concentration in soils varies between 2 and 23 ppm , and oceans contain about 0 @.@ 5 – 0 @.@ 8 parts per trillion . Distribution of samarium in soils strongly depends on its chemical state and is very inhomogeneous : in sandy soils , samarium concentration is about 200 times higher at the surface of soil particles than in the water trapped between them , and this ratio can exceed 1 @,@ 000 in clays . 
