Lead has four stable isotopes. The usefulness of lead isotope studies is the fortunate result of a threefold coincidence. Historically, lead was one of the first metals mined. Thus, it occurs in artifacts associated with many historical places and periods. Technologically, lead was easily won from its major ore, galena, and was found useful in many forms such as alloys, pigments, cosmetics, medicines, glasses and glazes. Geologically, and most importantly, lead is one of the few chemical elements which varies markedly in its isotopic makeup according to its geological occurrence.