Calibre Mining and B2Gold Sign Definitive Joint Venture Agreement

B2Gold to Spend an Additional $6.0 Million to Earn a 70% Interest in Calibre's Primavera Gold-Copper Project and Surrounding Borosi Concessions in the Mining Triangle, Nicaragua

VANCOUVER, BRITISH COLUMBIA--(Marketwired - Sep 10, 2013) - Calibre Mining Corp. (TSX VENTURE:CXB) (the "Company" or "Calibre") is pleased to announce that the Company has signed a definitive Joint Venture Agreement (the "JV Agreement") with B2Gold Corp. ("B2Gold") granting B2Gold an option to acquire a further 19% interest in and to the Primavera Gold-Copper Porphyry Project containing a total of 322 km² of mineral concessions (together, the "Project") in north-east Nicaragua. Calibre currently controls a 49% interest in the Project, while B2Gold controls a 51% interest and is project operator. In addition to this joint venture with B2Gold, Calibre controls a 100% interest in 463 km² of mineral concessions in the Mining Triangle of northeast Nicaragua which includes the recent, high-grade gold discovery at the Montes de Oro Project.

The JV Agreement dated September 9, 2013 allows B2Gold to earn an additional 19% interest in and to the Project for a total interest of 70% by spending $6.0 million in additional project expenditures over 36 months (3 years). The JV Agreement supersedes and replaces the original Option Agreement between Calibre and B2Gold (entered into in June 2009 and amended in July 2010 and October 2010) which has now been terminated.

Greg Smith, President and CEO stated, "The signing of the Joint Venture Agreement with B2Gold is an important step forward for the Primavera Gold-Copper Porphyry Project. As previously announced, B2Gold has initiated a $2.0 million program on the Primavera Project to expand the existing high grade gold-copper mineralized zone and to locate additional gold and copper discoveries within the 322 km² Borosi mineral concessions. We are very pleased to have B2Gold as Calibre's partner in the Primavera gold-copper discovery and look forward to significantly advancing the Project under the JV Agreement."

Significant terms of the Joint Venture Agreement are as follows:

• Calibre has granted B2Gold an option (the "Option") to acquire an additional 19% interest in and to the Project for a total interest of 70% in the Project by incurring CDN$6,000,000 in additional exploration and development expenditures on the Property over 36 months (3 years). Each (12 months) of the Option B2Gold must incur a minimum of $1.5 million of exploration and development expenditures on the Property. Expenditures incurred by any date in excess of the aggregate amount of expenditures required to be incurred by such date shall be carried forward to the succeeding period or periods and qualify as expenditures for such succeeding period or periods.

• Upon the exercise of the Option by B2Gold, B2Gold and Calibre shall share all further exploration and development expenditures on the Property on a 70% (B2Gold)/30% (Calibre) basis. B2Gold will be project operator.

• B2Gold shall only get credit towards the CDN$6,000,000 in required expenditures to exercise the Option for expenditures incurred on the Property after April 24, 2013.

Calibre's New High Grade Gold Discovery at Montes de Oro

Calibre recently announced trench results including 7.1 g/t gold over 52.3 metres from the new, high-grade gold discovery at Calibre's 100% owned Montes de Oro project - see News Release dated August 15, 2013. Further sampling consisting of additional trenching, extensions to open ended trenches and an expanded soil grid has been completed and results are expected over the next few weeks.

About Calibre Mining Corp.

Calibre Mining Corp. is a TSX Venture Exchange listed company (TSX VENTURE:CXB) that is focused on the acquisition, exploration and development of gold, silver and copper deposits in Central America. The Company is focused on its 100% owned Riscos de Oro and Cerro Aeropuerto gold-silver deposits, the exploration program at the Montes de Oro high grade gold discovery, the exploration program at the Primavera gold-copper project in conjunction with B2Gold Corp. and the exploration program on the Rosita copper-gold-silver project in conjunction with Alder Resources Ltd. Major shareholders of Calibre include gold producer B2Gold and investment fund Sun Valley Gold.

Calibre Mining Corp.

Greg Smith, P.Geo., President and CEO

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.