Kilo Goldmines (CVE:KGL) unveiled Thursday what it called "encouraging" results from preliminary metallurgical test work on diamond drill core from its Adumbi gold deposit, part of the Somituri project in northeastern Democratic Republic of Congo (NYSE:DRC).
Overall recoveries were 94.2 percent for gold recovery in oxide and 96.2 percent for gold recovery in sulphide.
The company said fold recoveries for three oxide composite samples ranged from 92.2 to 94.3 percent by gravity concentration, followed by cyanide leach of the gravity tails.
The gold recovery for one sulphide composite sample, which originated at depth from a minor lithological formation, was 42.9 percent, while two other composite samples returned gold recoveries of 92.5 percent and 96.2 percent.
The company said it will undertake further testing to optimize overall recoveries, including conventional cyanide leach testing on gravity tailings to improve grind size and solution strength. UK-based Wardell Armstrong prepared composite samples and carried out the test work.
"The preliminary test work is very encouraging and indicative that in excess of 90% of the gold in the oxide appears recoverable by the simple process of gravity and cyanide leaching of gravity concentration tails," said president and CEO, Alex van Hoeken.
"Given that the recent Inferred Mineral Resource estimate concluded about 600,000 ounces of gold in oxide, most of which is contained within Adumbi Mountain and mineable by open-pit with a very low stripping ratio, the anticipated ease of gold recovery is expected to bode well for the project economics."
In mid-March, Kilo released an updated NI 43-101 resource estimate for its 71.25 percent-owned Adumbi deposit. The DRC-focused gold explorer said in the inferred category, at a cut-off grade of 0.5 grams per tonne (g/t) gold, the resource estimate comprises 35.6 million tonnes containing 1.87 million ounces of gold at an average grade of 1.63 g/t gold. Of this, 33 percent is attributable to oxide, while 53 percent is attributable to sulphide.
Hoeken added: "The gold recoveries in excess of 90% for two of the three sulphide samples are most encouraging in that the majority of the sulphide mineralization may also be amenable to gravity and cyanide leaching of gravity concentration tails, in particular when the third sulphide sample is referenced to its host lithology that represents less than 4% of the gold bearing rock types identified in the Adumbi Gold Deposit.
"Furthermore, the lower than expected Bond Mill Working Indices should have a favourable impact on the power and infrastructure requirements for the project."
Indeed, the Bond Mill Working indice for composite oxide was 10.5 kilowatt hours per tonne (kWh/t), below expectations, and the indice for composte sulphide was 11.3 kWh/t, also below estimates.
Bond Ball Mill Work indices tests were carried out on one composited oxide sample, and on one composited sulphide sample. The test work has not conclusively determined the indices for the various rock types hosting the gold, the company said, but preliminary indications are that they are "significantly lower than expected".
As a result, this means an unexpected positive for process selection while possibly lower than expected project power requirements will be realized.
For the metallurgical testing, Kilo submitted 191 samples of diamond drill core from seven drill holes. The four oxide samples cover a strike length of 480 metres and the three sulphide samples were selected over a strike length of 560 metres and to a maximum vertical depth of 275 metres below surface.
Kilo Goldmines is a Canadian gold exploration company that has over 7,000 square kilometres of Archaean Kabalian greenstone in the Kilo-Moto area of the DRC. It also has a joint venture with Rio Tinto (NYSE:RIO) on potential iron ore licences in north-eastern DRC