novel alkaline earth metal fluosilicates which are activated with divalent europium are disclosed corresponding to the formula : m . sub . 1 - x eu . sub . x . sup . 2 + si f . sub . 6 wherein o & lt ; x ≦ 0 . 2 and m represents at least one alkaline earth metal from the group of barium and srontium . these fluosilicates exhibit luminescent activities emitting sharp line radiation in the near ultraviolet region and are especially suited for producing black light , e . g ., within discharge lamps .