Application Example
Characterization of Platinum
Group Minerals
using the TESCAN Integrated Mineral Analyser (TIMA)
The platinum-group metals (PGM) consists of six elements – platinum, palladium, rhodium, iridium, ruthenium and osmium.
Chemical inertness, oxidation-resistance, biocompatibility, high melting temperature, good conductivity and electronic and
catalytic properties are unique properties that make PGM irreplaceable starting material in many specific applications.
The deposits in the Norilsk-Talnakh region of Northern Russia are the largest nickel-copper-palladium deposits in the world
and, the intensive mining activity in this region, positions Russia as the world’s second global PGM supplier. In addition to PGM
output, a by-product of this mining is nickel and copper extraction. Although the predominant elements are platinum and
palladium, the PGM-bearing minerals contain other metals such as Au, Ag, As, Bi, Cu, Fe, Ni, Sb, Sn, Te, etc. Identification and
quantification of PGM minerals by means of automated mineralogy, assessment of elemental distribution and texture related
properties such as grain size, mineral association, and liberation degree are critical for excavation, ore processing and further
geological investigations. In this application example the effectiveness of the separation process (gravity separation and hydro-separation) by comparison of PGM mineral content, both in concentrate and in tailings, is studied.
Sample and instrumentation
Two representative samples of sulphide
system also provides further texture
copper-nickel ore from the Norilsk
related information such as grain size,
deposit were prepared. One of them
mineral association, liberation degree,
was the concentrate after gravity sepa-
etc. Mineral classification relies on X-ray
ration and laboratory hydro-separation
spectra (EDS) primarily acquired by four
and the second one was the tailings
Premium Silicon Drift EDS detectors
after the separation. The samples of
and the back-scattered electron (BSE)
-71+45 µm fraction were embedded in
signal, although other signals such as
epoxy blocks, polished and coated with
secondary electron (SE) and cathodo-
10 nm of carbon.
luminescence (CL) can be also used
The TESCAN Integrated Mineral Analyser
to provide further information on the
(TIMA) based on a TESCAN VEGA3 LM
sample. The data were acquired using
microscope was used for acquiring
an accelerating voltage of 25 kV and a
the data. It is a SEM-based automated
beam current of 5 nA in a high vacuum
mineralogical solution capable of auto-
mode. The working distance was set
mated identification and quantification
to 15 mm. The applied pixel spacing
of minerals present in the sample. The
was 2 µm.
cc TESCAN Integrated Mineral Analyser
(TIMA FEG)
Analytical modules
The TIMA software provides three soft-
and assessing the effectiveness of the
Bright Phase Search is focused on a
ware modules for data acquisition and
separation process.
rapid search for a specific group of
processing –Modal Analysis, Liberation
Liberation analysis is dedicated for the
particles of interest, such as gold, heavy
Analysis and the Bright Phase Search
analysis of particles and grains in the
metals or just PGM, usually forming a
(BPS) module. Liberation Analysis and
sample and provides information about
small percentage of the total number
Bright Phase Search (BPS) were chosen
their size, density, texture, as well as
of particles in the sample.
for the characterization of PGM ores
mineral and elemental composition.
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Application Example
Characterization of Platinum Group Minerals using the TESCAN Integrated Mineral Analyser (TIMA)
Results
The goal of the separation process, com-
the Liberation mode contained more than
minerals in the concentrate was 8.6%. The
prising gravity separation and laboratory
20 different precious minerals, most of all
most abundant gangue minerals were
hydro-separation, was to obtain a con-
taimirite (Pd, Cu, Pt)3Sn, isoferroplatinum
sulphides (pyrite, chalcopyrite, pyrrhotite,
centrate enriched in PGM, gold, silver
(Pt, Pd)3(Cu, Fe), sperrylite PtAs2, tetrafer-
pentlandite), magnetite, chromite, and
and other precious metals. The sample
roplatinum PtFe, kotulskite Pd(Te, Bi) and
silicates (olivine, amphibole, pyroxene,
of the concentrate analyzed by TIMA in
many others. The total content of precious
serpentine). Grains of PGM and other
1a
1b
1c
cc Fig. 1: Bright particles containing platinum (minerals rustenburgite, sperrylite, zvyagintsevite) with BSE image of all phases
(a), bright phases only (b) and classified bright phases (c).
2
cc Fig. 2: Liberation of PGM grains in the sample of concentrate.
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Characterization of Platinum Group Minerals using the TESCAN Integrated Mineral Analyser (TIMA)
Application Example
precious metals were often 70-100%
PGM, Au and Ag with diameters up to 5
carbonates) minerals. Less than 0.1%
liberated, less associated in particles
µm were found.
of PGM, Au, Ag and others remained
with sulphides, magnetite, chromite and
Both modes applied during TIMA meas-
in the tailings. On the other hand, the
other minerals.
urement have shown that the separation
grade of precious metals reached only
Bright phase search mode was applied
process is very selective in separating
8.6% in concentrate, so it is necessary to
to a sample of tailings. Of the total num-
high density (PGM, precious metals,
apply a further separation process on
ber of 71849 particles, only 17 grains of
sulphides) and low density (silicates,
an industrial scale.
3b
cc Fig. 3: A sample of tailings acquired and processed by Liberation Analysis (a) and Bright Phase Search (BPS) module (b).
BPS module displays only grains with high backscattered electron contrast and their host particles.
Conclusion
An automated mineralogy solution using
separation process. Both Liberation
„„ Acknowledgement
the TESCAN Integrated Mineral Analyser
mode and Bright Phase Search proved
The samples for this study were provided
(TIMA) was used to characterize PGM
to be optimal tools for characterization
by the Gipronickel Institute JS, Laboratory
ores, describe relations among minerals
of feed, concentrate and tailings during
of Raw Material Geological and Techno-
and to evaluate the efficiency of the
the processing of different types of ores.
logical Studies, in St. Petersburg, Russia.
TESCAN ORSAY HOLDING, a. s.
Libušina tř. 21, 623 00 Brno - Kohoutovice / Czech Republic
www.tescan.com
(phone) +420 530 353 411 / (email) [email protected] / [email protected]
TESCAN ORSAY HOLDING reserves the right to change the document without notice. 2016.02.22
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