rubicline
... that rubicline was the first mineral discovered with rubidium as an essential constituent?
... that <b id="mwBJY"><a href="./Rubicline" id="mwBJc" rel="mw:WikiLink" title="Rubicline">rubicline</a></b> was the first <a href="./Mineral" id="mwBJg" rel="mw:WikiLink" title="Mineral">mineral</a> discovered with <a href="./Rubidium" id="mwBJk" rel="mw:WikiLink" title="Rubidium">rubidium</a> as an essential constituent?