It occurs naturally in the minerals leucite, pollucite, carnallite, zinnwaldite, and lepidolite, although none of these contain only rubidium and no other alkali metals.
ɪɾ əkˈɜːz nˈætʃɚɹəli ɪnðə mˈɪnɚɹəlz lˈuːsaɪt, pəlˈuːsaɪt, kˈɑːɹnɐlˌaɪt, zˈɪnwɔldˌaɪt, ænd lˈɛpɪdˌɑːlaɪt, ɔːlðˈoʊ nˈʌn ʌv ðiːz kəntˈeɪn ˈoʊnli ɹuːbˈɪdiəm ænd nˈoʊ ˈʌðɚɹ ˈælkəlˌaɪ mˈɛɾəlz.