SAN GREGORIO MINE GEOLOGY AND DEPOSITS

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SUMMARY

OMI's San Gregorio Mine is located in Northern Uruguay in the historic Minas de Corrales mining district 450 kilometres north of Montevideo by paved road. The Minas de Corrales district is located in the western third of the Isla Cristalina Belt. The San Gregorio operation has produced ore from several deposits or lodes (see figure for specific deposit names) hosted along the San Gregorio Shear that dips moderately steeply to the south and is observed to have about 10km of mineralized strike. All the lode gold deposits are associated with quartz-carbonate boudins along shear structures and the principal alteration assemblage is silica- carbonate-sericite-pyrite-chlorite-epidote. The Arenal open pit was the primary source of ore feed at OMI's San Gregorio plant from 2004 to 2009 but several of the other deposits including cut-backs at San Gregorio (East Extension) and Santa Teresa (East) have also been important sources of ore. Approximately 1 million ounces have been produced from the Minas de Corrales District since the San Gregorio plant was commissioned in 1997 by MinProc. To date all of the deposits have been mined as open pits however OMI is currently completing a feasibility study on an underground mining operation at Arenal Deeps which was discovered and converted into a NI 43-101 compliant mineral resource during 2008-2009.

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