Mining Intelligence and News
Uruguay

San Gregorio Mine

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Overview

Mine TypeOpen Pit & Underground
StatusClosing / Closed
Commodities
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
  • Transverse stoping
  • Room-and-pillar
SnapshotThe reorganization process has been ongoing since June 2018. In August 2018, Orosur Mining Inc. wholly-owned Uruguayan subsidiary, Loryser SA (“Loryser”), placed its San Gregorio mining operations under care and maintenance. Under the Loryser reorganisation proceedings, the term for credit verification ended in September 2018. The Creditors Agreement was ratified by the Court in September 2019. Since then the Company has focused its activities on the implementation of the Creditors Agreement, and the sale of the assets of Loryser.

As at May 31, 2024, Loryser had agreed and paid for the settlements with all of its former employees. It had finalised the reclamation and remediation works on the tailings dam and sold all of its remaining assets, including its plant and equipment, and is distributing the proceeds on a pro rata basis, to Loryser’s trade creditors via a Court approved paying agent.

Owners

SourceSource
CompanyInterestOwnership
Orosur Mining Inc. 100 % Indirect
Orosur Mining Inc. wholly-owned Uruguayan subsidiary, Loryser S.A. is Company’s primary operating subsidiary in Uruguay.

Deposit type

  • Mesothermal
  • Orogenic
  • Vein / narrow vein

Summary:

The deposits discovered by Orosur to date in the San Gregorio project area are considered to be typical of mesothermal vein-style, or orogenic-style gold deposits.

The deposits located along the east-west to northwest trending SGFS are, from west to east, the Santa Teresa deposits, the Polvorín deposit, the Ombú deposit, the San Gregorio deposit and the Arenal deposit. Zapucay and Argentinita deposits lie along the extension of the one fold and thrust fault system to the east, with similar age of SGFS.

Gold mineralization at SGGP has occurred as infill of brittle fractures within favourable host rocks such as zones of silicification and mafic units. Brittle fracture has occurred within these zones in response to local extensional tectonics created by the intersection of different trending faults, faults with dikes and changes in the attitude of the fault itself. Intense brittle fracture, silicification and quartz veining are apparent in higher grade zones. At least 3 phases of fracturing and veining can be recognised from drill core.

The gold deposits are generally hosted within basement granulite and amphibolite facies within the upper plate of a large thrust fault that defines the contact with the younger granites to the north. Pyrite is the dominant sulphide, and gold grade is directly proportional to the pyrite content. The gold at all deposits is fine, and visible gold is rare. Other potentially deleterious elements are in low concentrations.

The northeast trend to the mineralization is apparent within the granites to the north of the main thrust, where the Sobresaliente and Castrillón deposits are located. These deposits are approximately 5 km and 7 km north of the San Gregorio mine site respectively.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

Milling equipment has not been reported.

Processing

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Production

During FY 2019, the Company produced 3,029 oz gold from San Gregorio until the mine was put in care and maintenance.
CommodityUnits20192018201720162015
Gold oz 3,02927,58635,37135,77353,485
Silver oz 20,25528,34328,34133,174
All production numbers are expressed as metal in doré.

Operational metrics

Metrics20192018201720162015
Annual processing capacity 1.03 Mt1.03 Mt1.03 Mt
Stripping / waste ratio 3.31 3.38 2.47 3.18
Waste 2,517 kt3,154 kt2,283 kt3,766 kt
Ore tonnes mined 760 kt934 kt926 kt1,182 kt
Total tonnes mined 3,276 kt4,088 kt3,209 kt4,948 kt
Tonnes processed 875 kt979 kt1,013 kt1,212 kt

Production Costs

CommodityUnits20182017
Cash costs Gold USD 970 / oz **   829 / oz **  
Total cash costs Gold USD 989 / oz **   882 / oz **  
All-in sustaining costs (AISC) Gold USD 1,453 / oz **   1,228 / oz **  
** Net of By-Product.

Financials

Units20182017
Capital expenditures M USD 9.1   9.3  
Revenue M USD 37.1   44.2  
Gross profit M USD -1.1   4  

Heavy Mobile Equipment

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Aerial view:

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