Mine of Shinkolobwe

The uranium content at Shinkolobwe was exceptionally high due to a highly efficient concentration process in favorable geological conditions; the site was even called a "freak occurrence" because such rich ore deposits have not been observed anywhere else.

But what are the geological conditions to get such a location?

Large uranium deposits typically form in old, stable continental regions (shields and cratons) where rocks have not been deeply buried or strongly shifted for tens to hundreds of millions of years.

Sufficient uranium must be present in the parent or source material. This uranium is released through the weathering of uranium-rich rocks, often granites.

Water (often oxygen-rich groundwater) transports dissolved uranium (usually in a hexavalent form, which is highly soluble). When chemical or physical conditions change (e.g., through reduction, interaction with organic material, or sulfides), uranium precipitates as insoluble minerals (often in a tetravalent form). This creates concentrated deposits, sometimes with very high uranium content.

A porous host rock (such as sandstone or fault zones) and sufficient water flow are crucial for both transport and subsequent precipitation.

Pascal Brackman