taaffeite
... that taaffeite, one of the world's rarest gemstones, is the first mineral known to contain both beryllium and magnesium as essential components?
... that <b id="mwBQ0"><a href="./Taaffeite" id="mwBQ4" rel="mw:WikiLink" title="Taaffeite">taaffeite</a></b>, one of the world's rarest <a href="./Gemstone" id="mwBQ8" rel="mw:WikiLink" title="Gemstone">gemstones</a>, is the first mineral known to contain both <a href="./Beryllium" id="mwBRA" rel="mw:WikiLink" title="Beryllium">beryllium</a> and <a href="./Magnesium" id="mwBRE" rel="mw:WikiLink" title="Magnesium">magnesium</a> as essential components?