ˈbər.trənˌdīt noun
( -s )
Etymology: French, from E. Bertrand, 19th century Frenchman who first described it + French -ite
: a mineral Be 4 Si 2 O 7 (OH) 2 consisting of a beryllium silicate occurring in hard colorless or pale-yellow prismatic crystals (hardness 6-7, sp. gr 2.59-2.60)