Rio Tinto Exploration and Calibre Mining Initiate 2021 Exploration Program Including 5,500 Metre Drilling Campaign Prioritizing Prospective Near-Surface Copper and Copper-Gold Mineralization April 08, 2021 07:00 ET | Source: Calibre Mining Corp. Calibre Mining Corp. VANCOUVER, British Columbia, April 08, 2021 (GLOBE NEWSWIRE) -- Calibre Mining Corp. (TSX: CXB; OTCQX: CXBMF) (the “Company” or “Calibre”) is pleased to provide an update on the Borosi exploration project held under an earn-in option agreement between Rio Tinto Exploration (LSE:RIO) (“RTX”)...