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Geology Pinson is a Carlin-type gold system with micron-gold hosted in altered, fine-grained sedimentary rocks. Pinson is identical in character to the numerous other neighboring mines that are the source of the majority of Nevada's 7.0 million ounces of annual gold production. Mineralization at both the Pinson Project and the Getchell Mine are controlled and locally hosted by the Getchell Fault zone, which defines the eastern margin of the Osgood Mountains. Fine grain calcareous siltstone and shale of the Ordovician Comus and Cambrian Preble formations host the micron gold mineralization at Pinson. Gold occurs in de-calcified and locally silicified zones along high-angle fault zones, within collapse breccias, and as stratigraphic controlled replacement bodies within receptive host rocks adjacent to feeder faults. Production and Exploration History Pinson produced nearly 1.0 million ounces of gold from oxidized zones within Ordovician sediments prior to 2000. As with the early production from other major Carlin gold systems, Pinson's production was sourced from within the oxidized zone of the deposit using heap-leach and direct cyanidization extraction methods from shallow open-pits. The Cordex partners, through its operating company Pinson Mining Company, produced gold from Pinson from 1980 through 2000. In 2000, Pinson Mining Company (a wholly owned subsidiary of Barrick Gold) closed the mine due to low metal prices and exhaustion of open-pit oxidized reserves. Pinson Mining Company conducted an extensive exploration program from 1997 through 2003 at the mine. This included over 200 drill holes (70,000 meters) to evaluate the deeper underground potential of the property. Barrick's exploration identified several zones of gold mineralization extending beyond the existing pit limits with gold grades potentially exploitable via underground mining methods. Three of these target areas, the CX Deeps, Range Front, and Line Hole, have numerous drill hole intercepts grading in excess of 0.25 ounces per ton gold. These high-grade gold targets were the focus of Atna's initial exploration efforts to define mineral resources at Pinson. Atna's Phase 1 Drill Program Atna's Phase 1 program completed 30,000 feet of infill and step-out drilling and confirmed the continuity of high-grade gold mineralization in the CX and Range Front (RF) zones. Gold mineralization was encountered in every drill hole of the program with high-grade gold values in nearly all holes. Atna Resources Ltd. reported the results of its initial mineral resource estimate at the Pinson gold project in February, 2005. The mineral resource estimate is based on assay results from 236,000 feet of drilling in 401 holes including the 30,000 feet of drilling completed by Atna during its Phase 1 program. The estimate, supported by a SEDAR filed NI43-101 Technical Report, includes the Range Front (RF) and CX zones, which are two sub-parallel zones of mineralization 600 feet apart that dip below previously mined open pits. The first phase RF/CX report estimate calculated a measured and indicated mineral resources of 467,000 ounces gold and an inferred resource of an additional 1,270,000 ounces gold at a 0.20 ounce per ton gold cut-off. The resource was considered to be economically attractive and to warrant an underground program and more drilling to further develop the resource potential. Atna's Phase 2 Exploration and Resource Upgrade Atna collared an adit during the second quarter of 2005 from within the CX pit, to provide access for underground definition and exploration drilling. The Phase 2 program was designed to:
Atna encountered a strongly mineralized zone in the adit as it progressed towards the planned RF drill stations. Channel sampling in the tunnel walls defined a 35 foot wide zone grading in excess of 0.5 oz/ton gold. Underground drill stations were established to drill the zone encountered in the drifting. The 4th hole cut significant gold mineralization including 147.5 feet grading 0.97 oz/ton gold (press release, November 2005). Further drilling delineated a significant new zone of gold mineralization, which was named the Ogee zone after Charles Ogee, one of the original prospectors who discovered the Pinson property in the 1930s. Atna fulfilled its earn-in requirements in early 2006 and vested a 70% interest in the project having spent the required US$12 million and delivered an evaluation of the project to Pinson Mining Company (Barrick Gold). Resource calculations for the RF zone and the Ogee zone were updated to include drilling completed within the $12 million earn in expenditure. The following table shows the most recently revised resource estimates, which were announced in July 2007. Pinson Project Revised Resource Estimate (0.20 oz/ton Au cutoff)
The revised estimate results in a significant increase in the total gold resource and in the transfer of additional mineralization from the inferred category to the measured and indicated categories. The Measured + Indicated categories increased by 50% from 712,600 ounces to 1,063,000 ounces at an average grade of 0.42 ounces gold per ton (an increase of over 30%). Inferred resources increased by 9% from 1,053,700 ounces to 1,146,600 ounces with an average grade of 0.34 ounces gold per ton. This increase in the gold grade is primarily due to the higher grade Ogee zone mineralization and to the elimination of low-grade, waste tonnage as a result of the more detailed drilling in the upper RF zone. In April 2006, Pinson Mining Company notified Atna that it elected to back-in on the project under the terms of the agreement. The back-in requires PMC to spend US$30 million to continue exploration and development of the property by April 5th, 2009 to earn back to a 70% operating interest in the project. Cautionary Note to U.S. Investors This section uses the terms "measured", "indicated" and "inferred" resources. We advise U.S. investors that while these terms are recognized and required by Canadian regulations, the U.S. Securities and Exchange Commission does not recognize them. "Inferred" resources are uncertainty as to their existence, economic and legal feasibility. It cannot be assumed that any or all parts of an Inferred Mineral Resource will ever be upgraded. Under Canadian rules, estimates of Inferred Mineral Resources may not form the basis of feasibility or prefeasibility studies, except in rare cases. U.S. investors are cautioned not to assume that any or all parts of the mineral deposits in these categories will ever be converted into reserves. Photos
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