He has also left his position as a director of the company.
Eyi was previously the CEO of Tri-Star before becoming founding CEO of the Oman Antimony Roaster gold project, which is owned by the joint venture company SPMP in which Tri-Star holds a 40% stake.
He recently resigned from his role as SPMP CEO, with Jason Peers appointed as interim CEO.
Tri-Star is yet to announce Eyi's replacement as deputy chairman.