THE International Atomic Energy Agency (IAEA) has recorded 2734 incidents of illegally trafficked nuclear materials since 1995. Questions including What is the material? Where were the materials sourced? and Why is the material being trafficked? need to be answered in order to close trafficking routes and stop these materials falling into the wrong hands. To do this, the material is analysed by a suite of analytical techniques in order to form a characteristic nuclear forensic fingerprint. This can then be compared to a nuclear forensic database containing representative samples of known origin to find a match. One of the key limitations of these databases is within mine heterogeneity. Representative sample databases only contain few and often small physical samples which are assumed to accurately represent a large geographical area. An increasing number of studies have determined significant within mine variation in signatures, this in some cases is larger than the variation between two different sites. This study aims to test the heterogeneity of a set of nuclear forensic signatures within vein type uranium deposits at a selection of different geographical scales. Sample sets from South West England and the Berias region of Portugal are analysed to deduce if small database samples are actually representative of large mining areas. It is also tested if these signatures are modified by the first stage of the uranium processing route; acid leaching. The nuclear forensic tools focussed on in this study are uranium and gangue mineralogy, major and minor elemental analysis, REE patterns and uranium isotope ratios. In summary, significant heterogeneity was found at all geographical scales tested. This indicates that databases need to be regularly updated as a deposit is extracted, and should include a moving average and range in signatures per site rather than a single physical sample. Although significant heterogeneity was found, in most cases, by using a selection of signatures, individual mines could be separated. It was concluded that much of the within mine variation observed in the ore sampled could be transferred through acid leaching during processing. In most cases elemental impurity patterns were not significantly effected by acid leaching, but uranium isotope signatures were variably affected and could not be traced back to their parent ore.