Critical Mineral Resources plc chairman Christopher Lambert has left the board of directors with immediate effect.
The company said that the board was considering his replacement.
The Moroccan-focused company also announced the appointment of general manager Noureddine Sabraou as chief operating officer also with immediate effect.
Mr Sabraou is a geologist in the Moroccan mining industry and has held a number of senior roles for national and foreign companies including as general manager for operating mines in the industrial minerals sector.
He has also run his own geological and mining services business and he co-founded the Moroccan Association of Mining Companies.