ˈgad ə ləˌnīt noun
( -s )
Etymology: German gadolinit, from Johann Gadolin died 1852 Finn. chemist + German -it -ite
: a mineral mainly Be 2 FeY 4 Si 2 O 13 that is a source of rare earths and consists of a black or brown vitreous silicate of iron, beryllium, yttrium, cerium, and erbium (hardness 6.5-7, specific gravity 4-4.5)