Images
Formula: PdTe2
Telluride, melonite group,
forms a series with melonite,
palladium-bearing mineral
Crystal System: Trigonal
Specific gravity: 8.547 calculated
Hardness: 2 to 3
Colour: White
Environments
Igneous environments
Metamorphic environments
Hydrothermal environments
Merenskyite is a principal palladium bearing
platinum group mineral. There are six
platinum group elements,
iridium,
osmium, palladium,
platinum, rhodium and
ruthenium. They often occur together, and are often
alloyed with each other.
Merenskyite occurs typically in disseminated interstitial segregations of
copper-iron-nickel
sulphides and enclosing silicates. Associated minerals include moncheite,
melonite, kotulskite,
michenerite, sperrylite,
laurite, cooperite,
chalcopyrite, pyrrhotite,
pentlandite, pyrite,
chromite and magnetite
(HOM).
Localities
At Ken Shoot, Kambalda Nickel mines, Kambalda, Coolgardie Shire, Western Australia, the major
platinum minerals are sperrylite
and moncheite, and the major palladium
minerals are sudburyite, merenskyite,
stibiopalladinite,
palladoarsenide,
michenerite and
testibiopalladite;
palladium also occurs in solid solution in
palladian melonite. The presence of
sudburyite, moncheite,
merenskyite, michenerite,
testibiopalladite, and
palladian melonite in stringers and reaction zones indicates that their
formation may be related to postmagmatic processes, in particular metamorphic segregation of sulphides and the
interaction of ore sulphides with younger hydrothermal fluids
(EG 81.1218-1225).
At the Limoeiro mine, Campo Formoso, Bahia, Brazil, the effects of weathering in the
nickel, copper and
platinum group element deposit reveal a progressive alteration of the
abundant primary merenskyite in the
supergene reaction front of the deposit.
Pyrrhotite, chalcopyrite,
pentlandite and minor
platinum group minerals are typical of the fresh ore assemblage in
the primary deposit. Weathering has produced a
gossan cap about 3 m thick over the base metal sulphide-rich parts of the
primary ore. Weathering effects are apparent as deep as 50 m
with the oxidation of pentlandite and
pyrrhotite to produce violarite
and pyrite respectively. chalcopyrite
is more stable, beginning to alter at a depth of around 20 m. The
platinum group minerals start to alter at a depth of about 25 m
where merenskyite becomes
palladium-rich because much of the
tellurium has been released into the adjacent
goethite. With progressively more weathering towards the surface the
merenskyite appears partially dissolved and pseudomorphed by
goethite
(CM 54.755-778).
At Fortaleza de Minas, Minas Gerais, Brazil, the nickel,
copper and
platinum group element
sulphide deposit is hosted by komatiitic rocks of the
greenstone belt. The deposit comprises:
(i) a main orebody, which is metamorphosed, consisting mainly of sulphide ores of early magmatic origin, and
(ii) platinum group element-rich discordant veins which are hosted in late
faults that cross-cut the main orebody.
The platinum group element-rich ore is characterised by thin,
discontinuous and irregular veins and lenses of massive sulphides hosted by
serpentinite and talc
schist. It is composed mainly of
pyrrhotite, pentlandite,
chalcopyrite, magnetite,
carbonates and amphiboles, with minor
cobaltite–gersdorffite,
sphalerite, ilmenite,
quartz, and rarely maucherite,
tellurides and
platinum group
minerals. Omeiite, irarsite,
sperrylite and nickel-bearing
merenskyite are the main platinum group minerals, followed by
minor amounts of testibiopalladite and an unknown phase containing
ruthenium, tellurium and
arsenic. The platinum group
minerals occur either included in, or at the margins of, sulphides, sulphosalts, silicates and oxides, or filling
fractures in pyrrhotite,
pentlandite and
chalcopyrite, suggesting that they started to precipitate with these
minerals and continued to precipitate after the sulphides were formed
(CM 45.751-773).
At the Elatsite Mine, Etropole Municipality, Sofia Province, Bulgaria, the
porphyry-copper deposit contains
platinum group minerals associated with base-metal sulphides,
including merenskyite, moncheite and
palladoarsenide, in a
magnetite–bornite–chalcopyrite
assemblage. Other minerals, including linnaeite,
carrollite, siegenite and
rammelsbergite, which are uncommon in typical
porphyry-copper deposits,
but occur here,
indicate a mantle derivation for this
platinum group element –
cobalt–nickel episode of
mineralisation
(CM 43.1355-1372).
At the Giant Mascot Mine, Hope, New Westminster Mining Division, British Columbia, Canada, the
nickel - copper -
platinum group element deposit is a deposit where the host rocks
are characterised by abundant
orthopyroxene and magmatic
hornblende. The Giant Mascot intrusion is composed of
ultramafic
olivine-orthopyroxene and
hornblende-clinopyroxene that
intruded an earlier dioritic pluton. The ores consist of
pyrrhotite, pentlandite,
argentopentlandite,
chalcopyrite, minor pyrite,
troilite, and
platinum - palladium -
nickel
bismuthotellurides
(EG 111.57-87)
At the McBratney prospect, Bear Lake, Flin Flon District, Manitoba, Canada, the high-grade
platinum group element –
gold
occurrence is hosted in
chlorite-actinolite and
chlorite schist. The
metamorphosed host rocks are komatiitic and
tholeiitic in composition. The occurrence comprises veins of massive
sulphide with variable amounts of quartz, carbonate,
clinochlore, chamosite,
biotite, muscovite and a variety
of platinum group minerals. The sulphides are mainly
chalcopyrite, pyrrhotite and
pyrite, with minor violarite,
pentlandite, bravoite,
marcasite, sphalerite,
galena, millerite and
cobaltite–gersdorffite.
Magnetite, coloradoite, and
gold–silver alloys occur locally. The
platinum group minerals include, in order of abundance,
tellurium-rich sudburyite,
borovskite, an unknown palladium
telluride–antimonide,
sudburyite, sperrylite,
temagamite and merenskyite. They are commonly found as inclusions
in chalcopyrite, pyrite and
carbonate, and are partially replaced by
cobaltite–gersdorffite. Minor
amounts of platinum group elements also occur within
chlorite, carbonate, and
stilpnomelane, and a
gold-silver alloy is observed locally
included in iron sulfides in association with
sphalerite. It is suggested that the mineralisation is hydrothermal, and
later than the regional metamorphic event. The platinum group
minerals precipitated coevally with the
nickel–iron–copper
sulphides, chlorite–chamosite,
biotite, carbonate and quartz
at temperatures ranging from 250° to 350°C
(CM 42.667-681, EG 105.1469-1490).
Near Rathbun Lake, Kawartha Highlands, Ontario, Canada, platinum,
palladium and gold are concentrated
in a hydrothermal copper-nickel
sulphide occurrence. The mineralisation is associated with a sheared zone of an intrusion where hydrothermal fluids
have altered olivine-poor gabbro
to chlorite, sericite,
quartz, epidote and
biotite. chalcopyrite and
pyrite, the principal sulphide minerals, occur as massive and disseminated
mineralisation. Bismuth-bearing merenskyite and to a lesser extent
kotulskite, michenerite and
temagamite are the
palladium-bearing minerals, whereas
platinum occurs primarily in
sperrylite
(EG 81.1272-1277).
At the Shebandowan Mine, Hagey Township, Thunder Bay District, Ontario, Canada, merenskyite occurs in
chalcopyrite and pyrrhotite
from copper-rich ore. Grains enclosed by
pyrrhotite are nickel-rich,
whereas those in chalcopyrite are
copper-rich
(CM 16.659-663).
At the Raglan Mine, Raglan, Nunavik, Nord-du-Québec, Québec, Canada, the most abundant
platinum group mineral is
sperrylite,
comprising a third of all the grains. Sudburyite and
merenskyite make up the majority of the remaining
platinum group minerals,
with minor constituents including moncheite,
temagamite and probably
hollingworthite. The majority of the
platinum group minerals are associated with sulphides and are either
completely enclosed within the sulphides, or at a sulphide–silicate boundary.
Platinum-bearing minerals are the predominant
platinum group minerals associated with
pyrrhotite and pentlandite in
monosulphide solid solution ores. In addition, the
platinum group minerals
in chalcopyrite-rich ores are commonly
platinum-bearing, with
palladium-bearing
platinum group minerals concentrated in
secondary veins
(CM 42.485-497).
At the Wellgreen deposit, Kluane District, Whitehorse mining district, Yukon, Canada, many
platinum group minerals are associated with base-metal sulphides in
the
nickel – copper –
platinum group element deposit. Various solid
solutions occur in this deposit:
(1) palladoan melonite–merenskyite–moncheite
(2) testibiopalladite–michenerite
(3) sudburyite–kotulskite–sobolevskite
(4) breithauptite–sudburyite
The associated platinum group minerals and
platinum group element-bearing phases include
sperrylite,
stibiopalladinite, mertieite,
geversite,
tetraferroplatinum, native
platinum, isoferroplatinum,
froodite (?), hollingworthite,
laurite, native iridium,
rhodium-bearing
cobaltite–gersdorffite and
palladium-bearing ullmannite
(CM 40.651-669).
At Genina Gharbia, Eastern Desert, Red Sea, Egypt, the intrusion is a small
mafic–ultramafic complex
comprising harzburgite,
lherzolite, pyroxenite,
norite and gabbro. The
intrusion is not metamorphosed, but highly affected by faulting and shearing. The rocks have a high content of
magnesio-hornblende and abundant
phlogopite and fluorapatite.
The copper–nickel ore forms either
disseminations in peridotite or massive patches in
gabbro, and consists of
pyrrhotite, pentlandite,
chalcopyrite, pyrite,
violarite, cubanite and minor
cobaltite–gersdorffite,
nickeline, sphalerite,
molybdenite and valleriite.
Platinum group minerals are restricted to bismuthotellurides of
palladium, including michenerite
and the melonite–merenskyite series; no
platinum minerals were identified. The
platinum group minerals are usually associated with
hessite, altaite,
tsumoite, sylvanite and native
tellurium. Ninety percent of the
platinum group minerals and other
telluride grains are located at sulphide–silicate contacts and as inclusions
in altered silicates
(CM 42.351-370).
At the Kevitsa mine, Kevitsansarvi, Sodankylä, Lapland, Finland, the deposit is a low-grade dissemination of
nickel–copper sulphides containing
platinum group elements. It is hosted by
olivine wehrlite and
olivine websterite,
metamorphosed at greenschist-facies conditions.
The sulphides consist of intergranular, highly disseminated aggregates mainly made up of
pentlandite, pyrite and
chalcopyrite, as well as
nickeline and gersdorffite
in some samples. Most platinum group minerals occur as single, minute grains
included in silicates or attached to the grain boundaries of sulphides. Only a few
platinum group mineral grains are included in the sulphides.
Platinum minerals, mainly moncheite
and sperrylite, are the most abundant
platinum group minerals, whereas
palladium minerals, mainly merenskyite,
palladian melonite,
kotulskite and sobolevskite,
are relatively scarce, and most contain
significant amounts of platinum
(CM 40.377-394).
At Varallo Sesia, Sesia Valley, Vercelli Province, Piedmont, Italy, melonite,
merenskyite and moncheite occur as minute grains dispersed within
pyrrhotite, pentlandite and
chalcopyrite. Electron microprobe analyses indicate that
melonite and merenskyite cover the whole range of
nickel-palladium substitution,
confirming the existence of a complete solid solution between these phases
(EG 81.1213-1217).
At the Fedorovo-Pansky massif, Murmansk Oblast, Russia, the layered mafic intrusion has an
olivine-poor
gabbro
zone that hosts
copper - nickel -
platinum group element
mineralisation with disseminated sulphides, mainly pyrrhotite,
chalcopyrite and pentlandite.
The mineralisation is palladium-rich and the most common
platinum group minerals are merenskyite,
moncheite, kotulskite,
sobolevskite and michenerite;
less common are sperrylite and
vysotskite-braggite. The
copper - nickel -
platinum group element
sulphides are primarily magmatic in origin
(EG 97.1657-1677).
At the Aksug copper-molybdenum
deposit, Todzhinsky District, Tuva, Russia, the ore-bearing porphyry
complex developed in intrusions of
gabbro-diorite-plagioclase
granite. Palladium
mineralisation occurs in massive chalcopyrite veinlets in zones of
intensely propylitised rocks. A study of
palladium-rich ores on a scanning electron microscope showed 2–5 micron sized
merenskyite inclusions in chalcopyrite. The merenskyite is
associated with electrum, monazite,
cobaltite, tennantite and
strontium-bearing baryte
(CM 48.656-658 ).
At the Uitkomst Complex, Waterval, Nkangala District, Mpumalanga, South Africa,
platinum group elements dominated by
palladium are present in the
nickel-copper-cobalt
bearing massive sulphide ore. The mineral assemblages here are indicative of formation temperatures probably less than
490°C. The distribution of the individual phases recorded for the deeper part of the ore body indicates an increase in
michenerite grains towards the base of the zone, an antipathetic
relationship between merenskyite and michenerite, and a
concentration of testibiopalladite grains at the top and the base of
the zone. The platinum group mineral grains are preferentially associated
with pyrrhotite and generally located along grain boundaries
(South African Journal of Geology 104.287-300).
The type locality, the Merensky Reef, Bojanala Platinum District Municipality, North West, South Africa, is an
ultramafic intrusive.
Melanorite, leuconorite and
anorthosite contain a
platinum group mineral assemblage that is predominantly
moncheite and merenskyite. The
platinum group minerals are rarely enclosed by
chromite. All the
platinum group minerals are predominantly associated with base-metal sulphides and are likely to result from late,
low-temperature processes superimposed on the magmatic ones
(CM 42.423-437).
The main platinum group minerals in descending order of abundance are
braggite, cooperite,
moncheite, laurite,
kotulskite, merenskyite (4 vol %), a
platinum-iron alloy,
palladian electrum and
sperrylite. The remainder (less than 1 vol %) include
atokite, paolovite,
rustenburgite and mertieite.
The earliest platinum-palladium
minerals to crystallise from the sulphide liquid are platinum-rich, with the
replacement of cooperite by braggite,
and moncheite and merenskyite by
kotulskite, as evidence of a later
palladium metasomatism
(EG 77.1367-1384).
At the Aguablanca Mine, Monesterio, Badajoz, Extremadura, Spain, the
nickel – copper –
platinum group element
ore deposit has a magmatic origin, and has been reworked by later
skarn-related hydrothermal activity. Base-metal sulphides are associated
with gabbro and dolerite,
with fragments of pyroxenite and
peridotite. These rocks show a pervasive retrograde alteration with
an early overprint of actinolite,
chlorite, epidote,
albite, serpentine, followed by
later growth of talc , chlorite and
carbonates. The base-metal sulphides consist of pyrrhotite,
pentlandite and chalcopyrite,
overprinted by fluid-deposited pyrite
(CM 42.325-350).
At Arthrath, Aberdeenshire, Scotland, UK, the prospect occurs within a group of
mafic–ultramafic rocks
emplaced broadly synchronously with the later stages of
amphibolite facies metamorphism of metasedimentary
units. Platinum group elements associated with zones of
copper–nickel–iron
sulphide mineralisation have been identified. The palladium is hosted
primarily in merenskyite enclosed in base-metal sulphide
(CM 45.335-353).
At Talnotry, Newton Stewart, Dumfries and Galloway, Scotland, UK, arsenic-rich
magmatic sulphide mineralisation is hosted by a diorite intrusion. A
relatively abundant and diverse platinum group mineral assemblage is present
and is dominated by sperrylite,
irarsite and electrum, with subordinate
merenskyite, michenerite and
froodite
(MM 68.395-411).
At the Stillwater Complex, Montana, USA, the presence of a
platinum-iron alloy,
isoferroplatinum,
platinian
rhodium, rhodian platinum, palladian gold,
cooperite, laurite,
braggite, vysotskite,
moncheite, kotulskite,
merenskyite, sperrylite and
stibiopalladinite has been confirmed
(EG 71.1352-1373)
Back to Minerals