Johnson is also executive director of African Battery Metals, joining it in a rescue deal last month.
Johnson was formerly CEO of Metal Tiger and was also previously chairman at ECR Minerals, CEO at China Africa Resources, now Pembridge Resources and Metals NRG, and non-executive director at Greatland Gold, Thor Mining and Papua Mining, now Rockfire Resources.
Armadale director Nick Johansen said Johnson, as well as other directors, management and key stakeholders had participated in a recent strategic financing, which was "a testament to our shared belief in the potential of Mahenge Liandu and we look forward to providing further updates on its development over the coming months".