Pasofino says several holes contain broad intervals of pyroxene gneiss with sulphide minerals – this is encouraging as gold at the nearby Tuzon and Dugbe F deposits is hosted by a similar lithology.

Called Lewisian gneiss, it’s the oldest rock in the UK. It’s found in the northwest extremity of the Scottish mainland and the Western Isles. The gneiss’s new home is in our gardens, where it forms ...