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Pitarrilla Project, Mexico

  • Pitarrilla Technical Report

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Location and History

The Pitarrilla project is located on the eastern flank of the Sierra Madre mountain range in the central part of Durango State, Mexico. The major city of Torreon lies approximately 150 kilometers east of the project. Road access is good, with paved highways extending to within 20 kilometers of the center of the property. Silver Standard, through Silver Standard Durango S.A. de C.V., holds a 100% interest in the mineral rights to the approximately 29,680-hectare Pitarrilla claim block and has applied for an additional claim covering in excess of 100,000 hectares. The company also holds significant surface rights in the area.

Geology and Metallurgy

To date, five zones of economically significant silver mineralization have been identified on the property, with four of these zones being closely associated with a rhyolite flow-dome complex that caps a 600-meter thick package of Tertiary-age andesite, dacite and rhyolite volcanic rocks. This succession of volcanic rocks unconformably overlies folded marine sedimentary rocks of Cretaceous age, and is intruded by a complex system of rhyolite sills and dikes. These rhyolite intrusive bodies, which can be more than 100 meters thick, are a key rock type at Pitarrilla because most mineralization is either hosted in the rhyolites or in the enclosing brecciated host rock.

There are now two types of mineralization at Pitarrilla. The first is finely disseminated microscopic grains of silver minerals in iron stained rhyolite intrusive and volcanic rocks. The second is disseminated massive sulphide mineralization containing variable amounts of silver, iron, zinc, lead and copper sulphide minerals. Copper values generally average between 0.2% and 0.5% but can range up to 17% in individual samples. Lead and zinc values each can locally exceed 20%.

Throughout 2006, diamond drilling was focused on defining the limits of the Breccia Ridge and South Ridge deposits. One of the outcomes of last year's program was the discovery of massive sulphide mineralization located in feeder zones below Breccia Ridge. Some of this mineralization is associated with the flat lying contact between the volcanics and the underlying sediments. Other zones are structurally controlled and extend well down into the sediments. This past year we were very successful in expanding the known resource at Pitarrilla, and in improving the overall quality of the defined resources. A resource estimate completed in July, 2006 increased the measured and indicated resources to 234.3 million ounces of silver, which represents an increase of 249%, and increased the inferred resources to 192.1 million ounces of silver, which represents an increase of 47.5%. This was achieved through the completion of over 40,000 meters of drilling in 118 holes. Highlights from the South Ridge Zone include hole PD-92 which intersected 515 feet of 6.5 ounces silver per ton (157.0 meters of 223.0 grams silver per tonne); and PD-120 with 445.2 feet of 5.3 ounces silver per ton (135.7 meters of 183.3 grams silver per ton).

Drilling at Breccia Ridge was equally successful as demonstrated by hole PD-148 which cut 841.8 feet averaging 6.4 ounces silver per ton (256.6 meters averaging 220.0 grams silver per tonne); including 329.0 feet which contained 7.5 ounces silver per ton (100.3 meters containing 258.5 grams silver per tonne), 3.45% zinc and 1.50% lead. Other significant Breccia Ridge holes included PD-152 which intersected 534.8 feet of 6.7 ounces silver per ton (163.0 meters of 230.1 grams silver per tonne), including 51.5 feet of 49.8 ounces silver per ton (15.7 meters of 1,706.1 grams silver per tonne) 6.92% zinc, 6.00% lead and 5.57% copper; and hole PD-157 which contained an impressive 1,972 feet averaging 2.5 ounces silver per ton (601.0 meters averaging 86.7 grams silver per tonne), including 99 feet of 8.5 ounces silver per ton (30.2 meters of 291.5 grams silver per tonne), 5.85% zinc and 2.16% lead.

Project Scope and Plans

The 2007 exploration program at Pitarrilla calls for the continuation of the aggressive drilling program with 60,000 meters planned. At present there are five diamond drills working on the property, which will initially focus on in-fill and step out drilling at Breccia Ridge Zone and then on South Ridge Zone. Throughout the year, geological mapping and interpretation of the drill results will lead to the testing for new zones of mineralization. An underground ramp is currently being contemplated to access the deep mineralization for metallurgical sampling and definition drilling. Metallurgical studies will be ongoing with the objective of designing an economically feasible ore processing flow sheet.

For details on the reserves and resources of the Pitarrilla Project,view the current Resource Summary (312 kb pdf).