Radiation damage to crystal structures may be detected using thermoluminescence (TL). Quartz and feldspar grains separated from rocks that were once mineralized with uranium display an anomalous TL characterized by an increase in high-temperature TL relative to low-temperature TL. This anomalous TL may be detected by either examining the ratio of low-temperature TL to high-temperature TL or a graph of TL intensity versus temperature. One of these methods of comparison must be used to normalize the variation in the susceptibility of the samples to TL. Without this normalization, the variation in the susceptibility could mask the anomalous TL caused by mineralization. After a uranium-mineralized rock has been leached of uranium, this type of anomalous TL persists for geolog cally significant lengths of time. Consequently, TL may be used to identify formerly mineralized rocks. Studies of TL around uranium deposits indicate that this type of anomalous TL is present in rocks updip from migrating roll-type deposits (one in Texas and one in Wyoming), around the margins of a partly leached tabular deposit in Utah, and in leached outcrops above a vein-type deposit in Colorado.

TL may be a very practical prospecting guide; it is inexpensive, fast, and easy, requires little sample, and is a direct indicator of uranium mineralization rather than of a concomitant process. Further, Tl samples are less susceptible to contamination than other types of geochemical samples.

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