spelter: impure zinc containing about three percent lead and other impurities (especially in the form of ingots)
zinc: a bluish-white lustrous metallic element; brittle at ordinary temperatures but malleable when heated; used in a wide variety of alloys and in galvanizing iron; it occurs naturally as zinc sulphide in zinc blende
dark adaptation: the process of adjusting the eyes to low levels of illumination; cones adapt first; rods continue to adapt for up to four hours