Testing boosts resource at Pirquitas deposit

Sunshine Mining & Refining (SSC-N) has received encouraging results from preliminary metallurgical testing at its Pirquitas silver-tin deposit in Argentina.

Early results indicate that silver recoveries should range between 80% and 90%, using both gravity and flotation methods. Although metallurgical testing has focused on silver, tin recoveries of 40%-50% have been achieved through the same methods. Improving the tin recoveries will be the goal of future testing.

The testing began in June on a 3-ton composite sample collected from Levels 1, 2 and 3 of the underground workings. Other 1-ton samples are being collected from Levels 4 and 5. More testing will be conducted through the first half of 1997, along with other work connected with a bankable feasibility study.

“[The results] are solid confirmation that Pirquitas will be a large and economic producer,” says Sunshine President John Simko. He says the results go “a long way toward answering our questions concerning the potential economics of the project.”

The deposit is in the northwestern Argentine province of Jujuy, where drilling continues to delineate and expand the deposit.

Reverse-circulation drilling completed to date includes 35,780 ft. from surface and 7,265 ft. from underground. Among the highlights from the latest results are: 52 ft. grading 22.9 oz. silver per ton and 0.91% tin in hole 14; 88.6 ft grading 17.5 oz. silver and 0.15% tin in hole 20; 72 ft. of 34.4 oz.

silver and 0.16% tin in hole 22; 39 ft. of 60 oz. silver and 0.36% tin in hole 33; 39 ft. of 52.3 oz. silver and 0.96% tin in hole 39; and 141 ft. of 17 oz. silver and 0.43% tin in another hole.

This new data have resulted in an increase of the size of the deposit. Its measured and indicated resource now stands at 118.7 million oz. silver and 117.7 million lb. tin.

Mineralization is found in two main areas — the high-grade Oploca II zone, which contains 0.7 million ton of 31 oz. silver and 0.85% tin, and the main deposit, which contains 19.2 million tons grading 4.98 oz. silver and 0.27% tin.

Drilling on the property will continue, and the company plans to complete an additional 16,000 ft. of core drilling and 26,000 ft. of reverse-circulation drilling before the end of the year. Further stepout drilling, planned for 1997, will test previously producing structures to the east of the main deposit.