Crystals of chernovite, a uranium-rich mineral, were found by scientists in samples from old mine workings at Grandhome, on the northern outskirts of Aberdeen. This site, historically quarried for manganese, has been recognised by geologists for over two centuries. The findings were published by Professor John Parnell and Dr Joe Armstrong in the journal Geochemistry: Exploration, Environment, Analysis.
The study revealed that rocks from Grandhome contain uranium concentrations approximately 100 times higher than those typically found in Aberdeen granite. Samples from other parts of the city, including Cults and Dyce, did not show similar enrichment. Researchers have stressed that the discovery poses no safety concerns, with Professor Parnell explaining that the amounts are not dangerous and the deposit is too small and dispersed for economic value.
The significance of the find lies in the story it tells about geological processes from around 400 million years ago during the Devonian period. The team believes groundwater movement through the ancient granite landscape concentrated dissolved elements, which were then trapped in minerals like chernovite, a rare mineral also containing yttrium and other rare earth elements. This occurred at the boundary between the granite and younger sandstone deposits.
Professor Parnell likened the geological process to a 'tarte tatin', where interesting chemistry occurs at the interface between different rock layers. The study also noted unusually high levels of arsenic associated with the mineralisation, attributed to low-temperature surface processes.
Dr Armstrong highlighted the value of Aberdeen's rocks as a record of Earth's history, stating that discoveries like this enhance understanding of the complex processes shaping the landscape. While mining uranium in Aberdeen is not feasible, the deposit offers valuable evidence of mineral formation and evolution over geological time.
