TORONTO (miningweekly.com) – Significant precious-metal-grade assay results have been returned from samples taken at Mongolia, Bolivia and Canada-focused miner Prophecy Coal's recently acquired Pulacayo silver project, in Bolivia.

Prophecy on Monday said it was encouraged by the silver grades found in the sampling, while remarkable gold and indium grades opened a new dimension to the Pulacayo mining district, because, to the company's knowledge, no historic gold sales were known, or indicated, on available production records and indium had not previously been mentioned or evaluated at all.

Prophecy's team was analysing historic and current drilling and sampling records at Pulacayo to locate the source of the high-grade indium and gold mineralisation.

The recent reconnaissance-sampling programme of tailings piles material at Pulacayo indicated silver grades of up to 1 200 g/t, gold grades of up to 7 g/t and indium grades of up to 154.5 g/t.

The Pulacayo mine extracted ore mostly from the Tajo vein system – which was a high-sulphidation epithermal system, 2.5 km wide and 2.7 km long, and the main source of the historical ore ouput – to minimum depths of 1 000 m.

Prophecy currently had a diverse portfolio of projects, including coal mining and thermal power generation assets in Mongolia, as well as vanadium, molybdenum and copper exploration projects in Canada. The Pulacayo transaction opened the door for it to become a high-grade silver producer in the not too distant future.

The tailings piles were the remaining materials from processing ore, extracted from the Pulacayo mining district between 1850 and 1950. The ore was processed by a mill on site that had since been dismantled.

Twelve tailings piles were identified at the start of the mapping and sampling programme, including the Pero, Paca, Pacamayo, Flores, Candelaria and Rotchild tailings piles.

The assay results were derived from 299 samples from the 12 tailings piles, drawn at random locations on the top surface of those piles from small holes excavated systematically at 2 m spacings in the slopes of the piles from hand-dug or excavated trenches, all at depths of 1.2 m to 1.5 m. 

Prophecy encountered only modest amounts of clay, which potentially indicated reasonable metallurgical recoveries.

As a next step, Prophecy intended to conduct a drilling programme to determine the uniformity of tailings piles grades and a bulk sampling programme for metallurgical testing to calculate metals recoveries.

Further mapping had shown several additional tailings piles about 400 m to 10 km away from Pulacayo and the company intended to conduct sampling and, if appropriate, drilling and metallurgical testing programmes to determine the economic viability of those piles.