Orosur Mining: San Gregorio Deeps Underground Project - Resource Estimate & Update

Orosur Mining Inc. (“Orosur” or the “Company”) (TSX: OMI) (AIM: OMI), a South American-focused gold producer, developer and explorer is pleased to announce a revised resource estimate incorporating drilling completed by Orosur on the western extension of the San Gregorio Deeps project (“SG Deeps”).

SG Deeps is a development-stage project aimed at exploiting and potentially expanding the existing resources from the historical San Gregorio deposit, and which are located under and adjacent to the historic main pit.

Revised SG Deeps Resource Estimate

Approximately 3,000 meters of drilling was completed to further evaluate the extensions of the gold resources at San Gregorio during Q3 2015. Based on the results of this drilling, the 2011 geological model and resource estimate (reported in the 2013 Technical Report) were updated with the assistance of Mine Development Associates (“MDA”) of Reno, Nevada. The new resource estimate confirms an improvement over the previously announced resources, a summary of which is below:

San Gregorio Deposit Area Resources (May 2015)

For an open pit scenario, using a cut-off grade of 0.70 g/t gold, there is an indicated resource of 3,341,000 tonnes at 1.58 g/t Au for 170,000 oz of contained gold.

For an underground scenario, at a cut-off grade of 1.60 g/t Au there is an indicated resource of 1,034,000 tonnes at 2.80 g/t Au for 93,000 oz of contained gold.

The distribution of resources and mineralization below the historic open pits is illustrated on the following longitudinal section:

Longitudinal Section of San Gregorio Main Pit and East Extension

SG Deeps West Zone

An internal preliminary mining study has focused on evaluating alternatives to mining the mineral resources located under and adjacent to the historic San Gregorio pits. This work analyzed three recovery methods, including:

• Underground mining;
• Open pit mining; and
• Combination of open pit and underground mining.

Preliminary planning has focused on an initial project incorporating underground mining in the west area only, where higher grades shall provide the best economic parameters, minimize the initial capital investment and minimize pay-out times. The initial west area underground project would be expected to recover in the range of approximately 30,000 – 35,000 oz of gold.

Orosur now plans to prepare detailed mine designs and formalize an internal study to support a development decision to start underground mining in the west area only. The decision to potentially develop a further underground mine in the central area and an open pit in the east area are expected to be considered at a later stage and once the SG Deeps project for the west area has been advanced sufficiently. SG Deeps remains open at depth.

Ignacio Salazar, CEO of Orosur, said:

“Having updated our geological model and resource estimate at SG Deeps with the assistance of MDA, we are pleased to have confirmed and increased the resource estimates and are currently advancing the pre-development work. In addition, we have completed an internal comparison study between open pit and underground mining and expect to make a development decision commencing with an initial project based on underground mining in the west area only to recover approximately 30-35,000 oz. This approach is designed to optimize the cash flow profile and minimize the risks and financial exposure, whilst allowing the Company to take advantage of the experience it has gained and the equipment fleet which is in place from its current underground operation at Arenal. At the same time, SG Deeps has additional resources for expansion to follow this initial stage which will underpin our mine life in the medium term.”

Forward Looking Statements

All statements, other than statements of historical fact, contained or incorporated by reference in this news release, including any information as to the future financial or operating performance of the Company, constitute "forward-looking statements" within the meaning of certain securities laws, including the "safe harbour" provisions of the Securities Act (Ontario) and the United States Private Securities Litigation Reform Act of 1995 and are based on expectations estimates and projections as of the date of this news release. There can be no assurance that such statements will prove to be accurate, such statements are subject to significant risks and uncertainties, and actual results and future events could differ materially from those anticipated in such statements. Forward-looking statements include, without limitation success of exploration activities; permitting time lines; the failure of plant; equipment or processes to operate as anticipated; accidents; labour disputes; requirements for additional capital title disputes or claims and limitations on insurance coverage. The Company disclaims any intention or obligation to update or revise any forward looking statements whether as a result of new information, future events and such forward-looking statements, except to the extent required by applicable law.

About Orosur Mining Inc.

Orosur Mining Inc. is a fully integrated gold producer, developer and exploration company focused on identifying and advancing gold projects in South America. The Company operates the only producing gold mine in Uruguay (San Gregorio), and has assembled an exploration portfolio of high quality assets in Uruguay, Chile and Colombia. The Company is quoted in Canada (TSX: OMI) and London (AIM: OMI).

Qualified Person's Statement

The scientific and technical information related to the current assets of Orosur Mining in this press release has been reviewed and approved by Michael Schwabe, an Exploration Consultant who is a Qualified Person under NI 43-101 reporting guidelines. Mr. Schwabe is a graduate in Science, majoring in Geology from the University of Tasmania and is Fellow of the Australian Institute of Mining and Metallurgy, a Senior Fellow of the Society of Economic Geologists and a Professional Member of the Society for Mining, Metallurgy and Exploration. Mr. Schwabe has 47 years of professional experience in the field of mineral exploration, mine development and management.