Allanite is a silicate containing a large amount of cerium. It is usually black in color, opaque, and is related to epidote in form and composition. In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... General Name, Symbol, Number Cerium, Ce, 58 Chemical series Lanthanides Group, Period, Block _ , 6, d Density, Hardness 6689 kg/m3, 2. ... Epidote is a calcium aluminium iron sorosilicate mineral, Ca2(Al, Fe)3(SiO4)3(OH), crystallizing in the monoclinic system. ...