Definition of röntgenite in English:
röntgenite
(also roentgenite)
noun ˈrʌntjənʌɪtˈrəːntɡənʌɪtˈrʌntɡənʌɪt
Mineralogy A mineral containing the rare earth elements cerium and lanthanum, typically occurring as small yellow or brown crystals. Also "röntgenite-(Ce)."
Origin
1950s. From the name of Wilhelm Conrad Röntgen + -ite.