Lupaka Gold (LPK.TO) has announced the results of the metallurgical testwork on their Crucero gold project in Peru.
Leach times of 24 hours at a grind size of 80% passing 53 microns provided extractions of 60-65% for the Southern Composite (mainly consisting of arsenopyrite) having a 1.57 g/t gold head grade and 70-75% for the Northern Composite (mainly consisting of pyrrhotite) having a gold head grade of 1.24 g/t. Ultrafine grinding tests to 80% passing 10 microns on whole-of-ore samples increased extractions to 89% and 94% for the Southern and Northern composites respectively. This might indicate the company won’t likely do whole ore leach on a commercial scale.
We asked CEO Eric Edwards some additional questions which might help to clarify some things.
– Is the 60-75% recovery on the 53microns what you expected?
60% to 75% is in the range of what we expected for the low end tests. The met tests looked at all options, and the whole ore leach generated the lowest values and we expected it to generate the lowest values.
– The ultra-fine grinding tests look much better. Is it fair to assume you’ll focus on the 10microns-size from now on? And would it be fair to assume you’ll need three crushing and grinding stages to get to this size?
The ultra-fine grind is interesting in that we would first do a combination of gravity, flotation and magnetic separation. The concentrate subjected to ultrafine grind would be a small fraction of the total, something less than 15% mass pull. We have only looked at single stage crushing with two stage grinding to get to the flotation. We will look at how we can achieve commercial scale ultra-fine crushing in further tests, but the “ISA Mill” technology looks interesting for that application. The good news, ultrafine grinding is on a fraction of the total.
– Did you only do testwork in 24hour cycles?
We looked at the leach curve at up to 72 hours. Optimum is likely at around 48 hours, but more test work is obviously needed.
> Click here to read the press release
Disclosure: The author holds a long position in Lupaka Gold. Lupaka is a sponsor of the website. Please see our disclaimer for current positions.
