North of 60 Mining News - The mining newspaper for Alaska and Canada's North

Rockhaven Resources Ltd. April 18 reported that the latest results from ongoing metallurgical work returned improved gold recoveries from several of the mineralized zones at its road accessible Klaza property in southern Yukon.

These zones will be the focus of an updated mineral resource estimate that will incorporate the results from roughly 20,000 meters of additional expansion and in-fill drilling completed over the last couple of years.

"We are extremely excited about the opportunities provided by the results of this test program, which should greatly benefit overall Klaza project economics," said Rockhaven CEO Matt Turner.

Using equipment envisioned in a 2016 preliminary economic assessment for Klaza, the latest round of metallurgical results achieved 82 percent gold recoveries by flotation and cyanide leaching in the Eastern BRX Zone.

This zone currently hosts 2.4 million metric tons of inferred resource averaging 4.1 grams per metric ton (317,000 ounces) gold and 53 g/t (4.13 million oz) silver. Previous flotation test work in the Eastern BRX zone, however, did not produce saleable concentrates. Because of this, the gold and silver in Eastern BRX were not included in the PEA.

Eastern BRX, as well as the Western BRX and Central Klaza zones, responded very well to pre-concentration test work. Using dense media separation – a means of gravity concentration that uses a heavy fluid to float of light material and leaving the metals bearing material for further recoveries – the average gold grades more than doubled, with gold recoveries ranging from 87 to 98.2 percent.

Significant upgrading by dense media separation was achieved, with good recoveries in all zones aside from Western Klaza. Work is underway to perform bulk DMS followed by locked cycle flotation testing to evaluate performance of the overall flowsheet.

"The pre-concentration results and encouraging recoveries from the Eastern BRX Zone are potential game-changers for the project, allowing lower cut-off grades to be considered and the inclusion of the Eastern BRX Zone in future economic studies," said Turner.

The encouraging metallurgical results also bode well for expanding the gold-silver resource at Klaza.

Eleven gold- and silver-bearing zones have been identified within a 3,000- by 4,000-meters structural corridor. These zones have been tested to a maximum depth of 450 meters and are open for expansion.

The eastern portion of the project area comprises multiple, sub-parallel veins – Eastern Klaza, Eastern BRX, Pika, Stroshein, and part of the AEX zones – all of which are open towards the mostly untested Kelly porphyry to the east. Due to the limited drilling in this area of the project, only the Eastern BRX and the Pika zones were included in the latest resource estimate, completed in 2015.

Rockhaven said the most important targets, given their proximity to the known deposits, are new discoveries north of the Klaza Zone; the eastern projection of Eastern BRX; and Eastern Klaza, which is mineralogically similar to Eastern BRX, but has only been tested by widely spaced drilling.

"The Klaza and BRX zones are fully open to the east and, with the positive metallurgical results, will be a major focus of future exploration programs," said Turner.

Rockhaven anticipates publishing an updated mineral resource estimate for Klaza by early June. In preparation for the estimate, the Klaza and BRX zones were remodeled to incorporate approximately 20,000 m of additional diamond drilling completed in 2016 and 2017. The new estimate will utilize revised cut-off grades that reflect results from the 2018 metallurgical test program and include lower grade mineralization in the hanging walls and footwalls of the main veins, which was not modelled in the previous resource estimate.

–SHANE LASLEY