with review and consultation by Dr. David Dreisinger 13.1 Metallurgical Testing Details
Laboratory scale testing in 2013 and 2014 was performed by SGS and XPS under the
supervision of the Company’s independent metallurgical Qualified Person, John Eggert,
P.Eng., of Eggert Engineering Inc. with review and consultation by Dr. David Dreisinger of
the University of British Columbia. The metallurgical test programs were designed to refine
the process flowsheet and to improve recovery levels, particularly for the PGMs that are
contained within saleable concentrates. These test programs evaluated the effect of factors
such as grind size, pH, conditioning, the use of various collectors, flotation reagents,
dispersants and depressants on mineral recoveries and concentrate grades, magnetic
separation and modifications to the mineral processing flowsheet.
One of the key observations from this assessment was that the optimization of sulphide
flotation recovery varied based on the three major geological domains. In general, the
recovery of economic metals is highest from the Gabbro/Massive Sulphides domain,
followed by the Clinopyroxenite/Pyroxenite and then by the Peridotite. Testing has shown
that the material from each domain can be processed in the same circuit with variances
related to grind size, conditioning time, pH and the use of magnetic separation with the
majority of reagent selection applied across all the domains.
With recognition that a sizeable amount of the PGMs, particularly platinum, was not being
captured in the sulphide flotation process because it was finer-grained and associated with
the magnetic minerals magnetite and pyrrhotite, the Wellgreen team and its metallurgical
consultants conducted subsequent testing to evaluate the benefit of adding a magnetic
separation process to the flowsheet. Magnetic separation is a proven technology utilized in
many operating Ni-PGM mines. The magnetic separation process was successful in
capturing additional PGMs, nickel and copper through regrinding of a modest volume of
magnetic material followed by conventional flotation, particularly in the
Clinopyroxenite/Pyroxenite and Peridotite domains. This material is then combined with the
main sulphide concentrate thus improving overall primary flotation recoveries. In addition,
the remaining magnetic material may be amenable to additional secondary processing, TECHNICAL REPORT – WELLGREEN PGM-NI-CU PROJECT
Page 86
potentially adding to the recovery of conventional flotation (see flowsheet in Figure 13-1
below).
Figure 13-1 Proposed Metallurgical Flowsheet
As a result of the improved understanding of sulphide flotation on the different domains, the
Company conducted additional test work on the lower grade Peridotite domain which had
historically seen much less testing. These tests confirmed that increased recovery can be
achieved in Peridotite following the same general process flowsheet with the use of
flocculants, magnetic separation and a slightly finer grind size than the other two domains.
The recovery level estimates for the metals in each of the three metallurgical domains are
based on recovery versus concentrate grade curves selected from the extensive batch tests
and locked cycle tests for each domain completed on the project to date. As noted in Table
13-1, the highest recoveries are in the Gabbro/Massive Sulphides domain with very good
recoveries also attained in the Clinopyroxenites/Pyroxenites and Peridotites. In addition,
testing showed that recoveries were generally higher for locked cycle tests than the majority
of batch tests due to the recycling of the process material, which simulates the actual
process flowsheet from a mine.
Bench scale testing and locked cycle tests for Wellgreen demonstrate that conventional
sulphide flotation methods can be used to produce a high-value bulk Ni-Cu-PGM
concentrate. These mineral concentrates contain pentlandite as the main nickel mineral,
chalcopyrite as the main copper mineral, along with the PGMs and gold included in the
minerals sperrylite, merenskyite, sudburyite, and lesser known minerals. Testwork has also
demonstrated the possibility of producing high value separate Ni-PGM and Cu-PGM
concentrates.
https://www.wellgreenplatinum.com/pdf/Wellgreen_2014_Resource_Technical_Report.pdf