A way to determine, nondestructively, the purity or composition of an unknown material sample such as, for example, a sample of gold or silver of unknown purity. The procedure involves subjecting one end of an elongate sample of known length and weight to a temperature elevated relative to that of the sample and comparing the time-varying temperature pattern at the other end thereof during finite lengths of time with that of a known or identically-sized standard subjected to equivalent or the same conditions for an interval of time of the same finite length. The temperature of said other end can be monitored during the time heat is applied and/or after it is withdrawn.