Rubidium ions are often used in purple fireworks, and caesium is often used in drilling fluids in the petroleum industry.
ɹuːbˈɪdiəm ˈaɪɑːnz ɑːɹ ˈɔfən jˈuːzd ɪn pˈɜːpəl fˈaɪɚwɜːks, ænd sˈiːsiəm ɪz ˈɔfən jˈuːzd ɪn dɹˈɪlɪŋ flˈuːɪdz ɪnðə pətɹˈoʊliːəm ˈɪndʌstɹi.