rare earths 1999 61 1 r are e ar ths by james b hedrick domestic survey data and tables were prepared jason t collins statistical assistant the world production table was ronald l hatch lead international coordinator principal economic sources of minerals bastnasite monazite loparite lateritic ion adsorption clays 2 a moderately abundant group 17 elements composed scandium yttrium 15 lanthanides range in crustal abundance from cerium 25th most element 78 common earth s crust at 60 parts per million to thulium lutetium least about 0 5 part rock forming typically occur compounds as trivalent cations carbonates oxides phosphates silicates atomic number 21 is lightest it 31st with an average 22 soft lightweight silvery white metal similar appearance weight aluminum represented chemical symbol
