 Free cobalt ( the native metal ) is not found on Earth because of oxygen in the atmosphere and chlorine in the ocean . Oxygen and chlorine are abundant enough in the upper layers of the Earth 's crust to prevent the formation of native metal cobalt . Except as recently delivered in meteoric iron , pure cobalt in native metal form is unknown on Earth ( see below ) . Though the element is of medium abundance , natural compounds of cobalt are numerous . Small amounts of cobalt compounds are found in most rocks , soil , plants , and animals . 
