Term: spelter: impure zinc containing about three percent lead and other impurities (especially in the form of ingots)
Broader: 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 | Unrelated: thermostatics: the aspect of thermodynamics concerned with thermal equilibrium