Wellgreen Project Preliminary Economic Assessment ... - OTCIQ.com

Prophecy Platinum Corporation – Wellgreen Property – Project 50149-001
Regrinding of already liberated particles is not ideal and particularly in Ni ores with floatable gangue.
Typically, the grind is applied on streams with abundant middling particles, not on well liberated streams.
Furthermore, the benefit of a re-grind mill cannot be tested in a batch test, as the effect of re-grinding the
floatable silicates cannot be assessed without recycling these particles. It is especially the build-up of
floatable gangue in the cleaning circuit that plague the ability to control floatation and attain an acceptable
concentrate grade and recovery
Test F12 examined the effect of higher CMC and no regrind which resulted in better selectivity. Ni grade
and recovery increased to 8% and 48%, however copper recovery decreased to 79%.
The effect of guar gum as a possible floatable silicate depressant was tested in test F13. While the
copper grade increased to 21%, Ni recovery was the worst at 8%. PGE recoveries were also very low in
this test.
Calgon was tried in test F14. Very low copper grade was achieved in this test. A combined 8% Cu/Ni, 8
g/t PGE, and 17.5% MgO were achieved in this test
To reduce Ni and PGE losses, CMC and guar gum dosages in the 2 nd and 3 rd cleaners were decreased in
tests F15 and F16. The results show the improvement of the recovery of Ni and PGE.
Tests F10 to F17 were conducted to investigate the effect of silicate depressants and optimize their
dosages by balancing these depressant to obtain good flotation performance. Mineralogy data indicated
the presence of free floating silicates which was countered with CMC as a depressant. The addition of
high dosage of CMC proved detrimental to both copper, and especially nickel recoveries.
Flotation tests F19-F21 tested the effect of a coarse primary grind at different re-grind sizes. Loss of Cu,
Ni and PGE in the rougher tailings resulted in lower recoveries.
The position of the regrind mill after the first cleaner was investigated based on the results obtained with
this configuration and with rougher concentrate re-grind. First cleaner concentrate was re-ground in test
F22 which resulted loss of Ni in the second cleaner tails.
In order to improve Ni recovery and enhance pyrrhotite distribution in the bulk concentrate, the effect of
CuSO4 was examined in flotation test F23. It was added after the collection of two rougher concentrates
at 175 g/t in the rougher and 70 g/t in the cleaner stages. Copper sulphate had no positive effect on Ni
and pyrrhotite recovery in this test.
Test F25 was conducted to adjust CMC dosages in the cleaner stages with no success due to high
dosages. The CMC dosages worked out to be ~600, 600, 800 g/t stage which were too high. Ni recovery
was very low in this test. At the start of the cleaners in this test a heavy froth was noticed which is a sign
of too much collector. In the roughers gangue is floated with the sulphides and the gangue helps support
the froth, however when CMC is added it depresses the gangue and the gangue no longer helps support
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