Orosur Mining Inc. – Gold Mineralisation Confirmed at Charrascala Target, Colombia

Orosur Mining Inc. ("Orosur” or "the Company”) (TSX/AIM: OMI), a South American-focused gold producer, developer and explorer is pleased to announce the final results from the recently completed gold exploration campaign at its high grade Anzá project in Colombia. Having confirmed consistent gold mineralisation in the APTA portion of the Anzá project in the first 18 holes of the exploration campaign, the final 5 holes of the drill programme were focussed on maiden scout drilling the untested Charrascala target. Drilling detected the presence of strong gold anomalies, with 4 of the 5 holes drilled intersecting gold mineralisation and a priority follow up zone has been identified.

HIGHLIGHTS

• Orosur successfully drilled 5 scout diamond drill holes totalling 3,045m at Charrascala, one of the four untested targets of Anzá;
• The presence of gold in the system has been confirmed within an attractive geological setting for the mineralization to occur;
• The presence of strong gold anomalies has been detected at Charrascala along an 800m north-south corridor, including intersects of 3.43 g/t Au and 30.60 g/t Ag over 1.5m and 2.62 g/t Au and 14.30 g/t Ag over 0.90m;
• Arsenic has been validated as a good gold pathfinder at Charrascala;
• Current drilling has identified an important exploration target in the south of Charrascala; which will be the priority for follow up drilling;
• Next exploration stages will be focused on continuing the broader exploration of the Anzá project and more detailed follow up and definition work at APTA.

Ignacio Salazar, CEO of Orosur, said:

"We are very encouraged with the recently completed exploration campaign at APTA and Charrascala in Colombia. Drill results at APTA have extended the mineralized area at depth and along strike, while still remaining open. APTA represents only 10% of the land base of the Anzá project, which covers over 200km². Additionally, in the last phase of this exploration campaign, the Company successfully tested the Charrascala target, discovering the presence of gold anomalies along an 800m north-south corridor, including an intersect of 3.43 g/t Au and 30.60 g/t Ag over 1.5m, as well as identifying a specific target for future drilling. The Company’s future in Colombia is looking to be off to a promising start.”

In addition to the APTA discovery, the Anzá project contains four additional untested high priority targets with coincident geochemical and geophysical anomalies (Fig. 1). One of them, Charrascala, is located approximately 1.5 km to the west of APTA. Charrascala is defined by an extensive coincident gold-in-soil anomaly and a geophysical anomaly that is approximately 3 km north-south by 1 km east-west and localized along a likely north-south structure. Surface mapping and sampling combined with interrogation of geophysical data sets share similar attributes to APTA, which have been validated by recent drilling.

The current exploration campaign started in October 2017 at APTA, where Orosur completed 18 holes (MAP_54 to MAP_71) totalling 6,314m. Assay results from these holes have been published in separate press releases dated February 20, 2018 and April 4, 2018. Following the successful results at APTA, Orosur has now completed the last portion of this campaign with a further five drill holes at Charrascala (Fig. 2) aimed at testing the Charrascala geochemical anomaly and gaining further insight to the stratigraphy of the sub-sector.

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Table 1. New assay results from the Charrascala drill program, Anzá project

Scout drilling at Charrascala intersected gold occurrences along an 800m north – south structural corridor. These mineralized intercepts range between 0.90m up to 3.8 m in thickness and are characterized by brittle veinlet zones with high sulphide content, mostly pyrite, with minor pyrrhotite, chalcopyrite and sphalerite. Hydrothermal alteration includes intense silicification and propilization which tend to reflect the presence of structures that controls mineralization. The host rocks are intermediate to mafic volcanic flows, tuffs and breccias of the Barroso Formation. The Barroso Formation is part of the igneous-sedimentary sequence that hosts many of the important mineral deposits of the Cauca Gold Belt, including the Buritica deposit.

Table 2. Hole location and orientation for the new holes assayed to date.

Trace element geochemical analysis from drill core at Charrascala show a positive correlation (r = 0.60) between gold (Au) and arsenic (As) values. This correlation provides a useful surface exploration tool that may be applied at Charrascala and the whole Anzá area to target additional gold mineralization. At Charrascala, soil sampling has revealed a large arsenic anomaly, with scattered Au values located immediately towards the south and south-east of the recognized area, close to Guaimarala (Fig.3). The anomaly is associated with a NW regional trending structure and it is a priority target for a future drilling campaign, together with other arsenic and gold anomalies at APTA.

To view the full release, showing all maps and figures, please click here.

Based on the interpretation from drilling results, geologic mapping, soil geochemistry and geophysical surveys, gold mineralization occurs within a geological setting comprising an important structural domain, a well-developed alteration mineral suite, with an important Au-As geochemical correlation, lying within the favourable regional Barroso Formation host rocks of the Cauca Belt, the prolific gold trend of western Colombia. This combination of key indicators will guide future exploration and drilling within the Anzá Project area needed to discover and delineate additional new gold deposits similar to APTA and other styles recognized in the Cauca Belt.

Next steps

Based on the current status of the exploration at the Anzá Project, the Company envisages two immediate objectives for future exploration campaigns: 1.) a regional surface exploration effort oriented to more fully understand the implications of the soil geochemical and geophysical anomalies at Anzá and bring them to an early drilling stage, and 2.) continue and expand the deposit definition drilling at APTA.

Quality Control and Reporting Protocols

This initial drill program recovered HQ/HQ3 core which was logged, split in half for sampling, with the remainder stored for reference in the secure core facility at Finca El Vergel, Anzá, Antioquia, Colombia. Samples are delivered to SGS lab and ALS lab both in Medellín, Antioquia, Colombia (ISO/IEC 17025), for analysis. At the Laboratory, samples are analyzed for gold by traditional fire assay with atomic absorption finish, with those samples returning >5 g/t gold repeated using a 50g aliquot and gravimetric finish. Samples are also analyzed for multi-elements including silver, cobalt, copper and zinc by total digestion ICP at the same labs. Selected samples will also be re-assayed by metallic sieve methods using up to a 350 g aliquot, based on gold and sulfide content.

Drill program design, Quality Assurance/Quality Control ("QA/QC”) and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards, duplicates, and blanks are added at the lab as well as standards, blanks and duplicates submitted as unknowns by the Company approximately every ten samples. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.

Assays are reported as composited intervals using length weighted averages, with highly enriched zones reported separately. Assays are uncut at this time. Applicable true widths are determined by ongoing investigation of the continuity and geometry of zones and are typically expected to be 65% to 85% of the reported core lengths.

Qualified Person

The technical information related to the current assets of Orosur Mining in this announcement has been reviewed and approved by independent Mining engineer Miguel Fuentealba, a qualified person as defined by National Instrument 43-101.

About Orosur Mining Inc.

Orosur Mining Inc. (TSX: OMI; AIM: OMI) is a fully integrated gold producer, developer and explorer 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 information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulation ("MAR"). Upon the publication of this announcement via Regulatory Information Service, this inside information is now considered to be in the public domain. If you have any queries on this, then please contact Ryan Cohen, VP Corporate Development of the Company (responsible for arranging release of this announcement on behalf of the Company) on: +1 (778) 373-0100.

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.

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