Atna’s underground mine project has open-pit potential

Atna Resources (ATN-T, ATNAF-O) will start commercial underground mine production at its Pinson mine project near Winnemucca in the fourth quarter of this year, but in the meantime it’s also exploring the possibility of developing an open pit mine on the property based on a maiden open-pit resource estimate.

Atna released its first open-pit resource estimate on Feb. 6 and says it will undertake a feasibility study while the company ramps up for underground production. Measured and indicated resources for an open pit at Pinson stand at 23.10 million tonnes grading 1.32 grams gold per tonne for 981,700 oz. of contained gold and inferred resources add 747,900 tonnes at a grade of 1.18 grams gold for 28,300 oz. contained gold.

Pinson’s underground resource currently stands at 2.65 million tonnes grading 12.60 grams gold for 1.07 million oz. of contained gold in the measured and indicated category and 2.03 million tonnes averaging 12.97 grams gold per tonne for 845,900 oz. contained gold in the inferred category.

Combined measured and indicated resource estimates for the high grade underground zones were largely unchanged from prior estimates in 2007, but inferred resources were slightly lower, the company says. The inferred underground resource was lower due to factors including the use of more conservative interpolation parameters based on a larger data set, the inclusion of additional data that changed geological interpretations in local areas, and the interaction with estimated open-pit resources.

Atna’s contract miner at Pinson is currently driving a secondary access and the company believes it can start mining bulk metallurgical samples during the next quarter.

The Pinson mine is in the south-central portion of Nevada’s Getchell gold belt southwest of Barrick Gold‘s (ABX-T, ABX-N) Getchell-Turquoise Ridge mines and Newmont Mining‘s (NMC-T, NEM-N) Twin Creeks mine complex.

Gold mineralization at Pinson is characterized as a Carlin-type, sediment-hosted gold system. Atna believes Pinson is hosted by the same sequence of Ordovician sedimentary rocks that hosts the gold deposits of Twin Creeks and Turquoise Ridge mines, according to its website.

Currently Pinson is permitted for underground mining under a small miner’s permit but Atna says it will soon submit applications to amend the permit to allow full-scale underground operations.

The ore from Pinson will be sent to nearby third-party plants for processing.

Should the company decide to develop an open pit mine at Pinson, additional permitting will be required, and may include an environmental impact study.

Pinson produced 985,000 oz. gold through open-pit mining and heap leach and oxide mill recovery between 1980 and 1999. Since 1998 the mine has seen more than US$60 million in exploration and development spending, according to Atna’s website. No resource estimate for the open-pit mining potential remaining at Pinson was ever completed until now.

News of the resource estimate failed to impress the market, however. Shares of Atna fell 8.77% or 10¢ to $1.04 per share with 2.1 million shares traded.

At presstime in Toronto Atna was trading at $1.02 per share within a 52-week range of 52¢-$1.15. The junior has 117.3 million shares outstanding.