 Cobalt is primarily used in the preparation of magnetic , wear @-@ resistant and high @-@ strength alloys . The compounds , cobalt silicate and cobalt ( II ) aluminate ( <unk> , cobalt blue ) give a distinctive deep blue color to glass , ceramics , inks , paints and varnishes . Cobalt occurs naturally as only one stable isotope , cobalt @-@ 59 . Cobalt @-@ 60 is a commercially important radioisotope , used as a radioactive tracer and for the production of high energy gamma rays . 
