assayer n : an analyst who assays (performs chemical tests on) metals
An assayer is a person who tests ores and minerals and analyzes them to determine their value and composition. They may use spectrographic analysis, chemical solutions, and chemical or laboratory equipment, such as furnaces, beakers, graduates, pipettes, and crucibles.
An assayer separates metals or other components from dross materials by solution, flotation process, or other liquid processes, or by dry methods, such as application of heat to form slags of lead, borax, and other impurities. Residues may be weighed on a balance to determine any proportion of precious metals or other components. Specialists in testing and analyzing precious metals are designated gold-and-silver assayer.