The method relies on the determination of the total amount of U, Th, and Pb in a mineral without isotopic analysis. This method is very old, and is also known under other names such as the chemical lead method, the alpha lead method, and the Larsen method. This author has shown in 1952 that, unlike minerals rich in U and Th, those in which they occur as trace elements (zircon, monazite, sphene, xenotime) are able to give good geochronological results. In effect, they do not incorporate any common lead at the time of crystallization, and make good closed systems in their resistance to alteration.