Orinoco Gold (ASX: OGX) has uncovered “spectacular” gold grades from samples at its pilot hammer mill, part of its 100%-owned Cascavel project in Brazil.
Four samples from the pilot hammer mill program returned gold grading 38.8 grams per tonne, 41.8g/t, 26.6g/t and 40.4g/t, with the average grade from 15 samples sitting at 48.6g/t.
“This ‘back to basics’ approach is an important step in showing Cascavel’s true potential as one of the higher grading gold mines in Latin America,” Orinoco chief operating officer Richard Crew said.
The back to basic approach was undertaken after initial mining failed to return low cost ounces due to “excessive dilution during mining” and “lower recoveries” from the gravity recovery plant.
As part of the back to basics approach, the company trialled a more traditional pilot hammer mill processing route for its ore, which revealed “dramatically improved” grades compared to the gravity recovery plant.
The hammer mill works by crushing the ore into smaller particles, allowing better recoveries for the project’s finer-grained gold.
The first trial was carried out between late November and mid-December and achieved more than 90% recoveries with gold grading between 30g/t and 149g/t.
According to the company, the 11 samples were taken from different areas within the mine.
This latest trial of 15 samples was conducted between 18 and 21 December, and revealed similar recoveries, with ore taken from Cascavel’s Mestre and Central zones.
“We are excited to take this pilot operation to a much larger scale hammer mill in January,” Mr Crew said.
However, the company cautioned the anticipated 30 tonne per hour hammer mill may not show the same recoveries as the smaller 200kg per hour operation the company just trialled, but initial results are positive.
Orinoco’s is also retesting the Northern zone, which had yielded previously “disappointing” gold through the gravity recovery.
Mining has restarted at the zone, with up to 10 samples to be processed through the hammer mill and results expected by mid-January.
“Work has also recommenced on the Northern zone of the orebody that was thought to be low grade, but could also show similar turnaround results that Mestre and Central have shown through the hammer mill,” Mr Crew said.
If the Northern zone results are similar to the previous two campaigns, Orinoco claims it will use the Northern zone as another ore source in 2018.
The company is also investigating the Cuca zone which sits under Mestre. Orinoco stated if Cuca and the Northern zone prove successful, the project could have four ore sources for feeding its larger hammer mill by the end of June 2018.
By late morning trade, Orinoco’s share price had surged more than 70% to sit at A$0.04.