Indicator minerals in prospection

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W O R K S H O P
Indicator mineral methods 
in mineral exploration 
Indicator mineral methods 
in mineral exploration 
 
Workshop 21 August 2011
25th International Applied Geochemistry Symposium 2011
22-26 August 2011 Rovaniemi, Finland
Beth McClenaghan, Vesa Peuraniemi and Marja Lehtonen
Publisher: Vuorimiesyhdistys - Finnish Association of Mining and Metallurgical 
Engineers, Serie B, Nro B92-4, Rovaniemi 2011
McClenaghan, B., Peuraniemi, V. and Lehtonen, M. 2011. Indicator mineral methods in mineral explora-
tion. Workshop in the 25th International Applied Geochemistry Symposium 2011, 22-26 August 2011 Ro-
vaniemi, Finland. Vuorimiesyhdistys, B92-4, 72 pages.
 
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Indicator mineral methods in mineral exploration
Beth McClengahan1, Vesa Peuraniemi2 and Marja Lehtonen3
1 Geological Survey of Canada, E-mail: bmcclena@nrcan.gc.ca
2 University of Oulu, E-mail: vesa.peuraniemi@oulu.fi
3 Geological Survey of Finland, E-mail: marja.lehtonen@gtk.fi
Abstract
This one-day workshop builds on the success of the indicator mineral workshop 
held at the 25th International Applied Geochemistry Symposium. This workshop 
will review principles, methods, and developments in the application of indicator 
mineral methods to mineral exploration. In the 1970s and 1980s, indicator mineral 
methods were used mainly for tin and tungsten and gold prospecting. Since playing 
a key role in the discovery of the Lac de Gras diamond field in northern Canada in 
the 1990s, indicator mineral methods have risen in prominence. The scope of the 
method has expanded, and the range of commodities being sought has broadened to 
include base and rare metals, as well as diamond and precious metals. The workshop 
consists of presentations by some of the most experienced practitioners in the field. 
Indicator mineral methods applied to exploration for gold, porphyry Cu, rare metals, 
magmatic Ni-Cu and diamonds will be presented as well as heavy mineral recovery 
methods, the application of Fe oxide mineral chemistry, and the value of sulphides 
and sulphate minerals. 
Workshop 3 Program 
Sunday, 21 August 2011, Hotel Santa Claus, Rovaniemi
8:30 - 8:45 am Registration
8:45 - 9:00 am Introduction
Beth McClenaghan and Vesa Peuraniemi (Conveners)
9:00 - 9:30 am Sample processing methods for recovery of indicator minerals from surficial sediments, 
Beth McClenaghan, Geological Survey of Canada, Canada
9:30 - 10:00 am Indicator minerals in diamond exploration: a case study from eastern Finnmark, 
Arkhangelsk and the Devonian Belt (Estonia, Lithuania, Novgorod and Pskov), 
Pavel Kepezhinskas, Kimberlitt AS, Norway
10:00 - 10:30 am Exploring for RE and REE mineralization using indicator minerals 
Marja Lehtonen, Geological Survey of Finland, Finland
10:30 - 10:45 am COFFEE BREAK
10:45 - 11:15 am Placer gold microchemistry in conjunction with mineralogy and mineral chemistry of 
heavy mineral concentrates to characterise bedrock sources
Norman Moles, University of Brighton, UK
11:15 - 11:45 pm Applicability of sulphide and sulphate minerals in heavy mineral studies, 
Vesa Peuraniemi, University of Oulu, Finland
11:45 - 1:00 pm LUNCH
1:00 - 1:30 pm Application of iron-oxide discriminant plots in mineral exploration, 
Georges Beaudoin, Université Laval, Canada
1:30 - 2:00 pm Porphyry Cu indicator minerals in glacial till samples around the giant Pebble Porphyry 
Cu-Au-Mo deposit, Alaska,
Bob Eppinger, US Geological Survey, USA
2:00 - 2:30 pm Heavy mineral assemblages in Devonian sandstones and Quaternary sediments in Latvia, 
Vija Hodireva, University of Latvia, Latvia 
2:30 - 2:45 pm COFFEE BREAK
2:45 - 3:15 pm Kimberlite indicator mineral based diamond exploration programmes in Karelia, 
North-West Russia, 
Vladimir Ushkov, Karelian Geological Expedition, Russia
3:15 - 3:45 pm Till indicator mineral and geochemical signatures of magmatic Ni-Cu deposits, 
Thompson Nickel Belt, central Canada, 
Beth McClenaghan, Geological Survey of Canada
3:45 - 4:00 pm Discussion and closing remarks
 
Content
Introduction
Beth McClenaghan & Vesa Peuraniemi
Overview of processing methods for recovery of indicator minerals 
from sediment and bedrock samples
M. Beth McClenaghan 1
Indicator minerals in diamond exploration: A case study from eastern 
Finnmark, Arkhangelsk and the Devonian Belt 
(Estonia, Lithuania, Novgorod and Pskov)
Pavel Kepezhinskas 7
 
Exploring for RE and REE mineralization using indicator minerals 
Marja Lehtonen, Jukka Laukkanen & Pertti Sarala 13
Placer gold microchemistry in conjunction with mineralogy and mineral 
chemistry of heavy mineral concentrates to characterize bedrock sources
Norman Moles & Rob Chapman 19
Applicability of sulphide and sulphate minerals in heavy mineral studies
Vesa Peuraniemi & Tiina Eskola 27
Application of iron-oxide discriminant diagrams in mineral exploration
Georges Beaudoin, Céline Dupuis, Beth McClenaghan, 
Jennifer Blain & Isabelle McMartin 35
Exploration case study using indicator minerals in till at the giant Pebble 
porphyry Cu-Au-Mo deposit, southwest Alaska, USA
Robert G. Eppinger, Karen D. Kelley, David L. Fey, 
Stuart A. Giles & Steven M. Smith 41
Heavy mineral assemblages in Devonian sandstones and 
Quaternary sediments in Latvia
Vija Hodireva & Denis Korpechkov 49
Kimberlite indicator mineral-based diamond exploration program 
in Karelia, northwest Russia
Vladimir Ushkov 57 
Indicator mineral signatures of magmatic Ni-Cu deposits, Thompson 
Nickel Belt, central Canada
M.B. McClenaghan, S.A. Averill, I.M. Kjarsgaard, 
D. Layton-Matthews & G. Matile 67
Indicator Mineral Methods in Mineral Exploration, Workshop 3, 1-6. 25th International Applied Geochemistry Symposium
The concentration of heavy minerals and recovery of indica-
tor minerals from surficial sediment is one of the oldest explo-
ration methods, being first applied to stream sediments in
Roman times. The application of indicator mineral methods to
mineral exploration has expanded and developed significantly
over the past two decades. They are now used around the
world to explore for a broad spectrum of deposit types includ-
ing kimberlites (diamonds), lode gold, magmatic Ni-Cu-PGE,
metamorphosed volcanogenic massive sulphides (VMS), por-
phyry Cu, uranium, tin, tungsten, and rare metals (e.g. Averill
2001). Indicator minerals, including ore, accessory and alter-
ation minerals, are usually sparsely distributed in their host
rocks. Indicator minerals may be sparser in derived sediments,
thus sediment samples must be concentrated in order to
recover and examine them. Most indicator minerals have a
moderate to high specific gravity, thus most processing tech-
niques concentrate indicator minerals using some method of
density separation, often in combination with sizing and/or
magnetic separations. The presence of specific indicator min-
erals in unconsolidated sediments provides evidence of a
bedrock source in the provenance region and in some cases,
the chemical composition of the minerals is associated with
the ore grade of the bedrock source. As few as one sand-sized
grain of a particular indicator mineral in a 10 kg sample may be
significant. To recover such potentially small quantities (equiv-
alent to ppb) of indicator minerals, samples are processed to
reduce the volumeof material that must be examined. In
reducing the volume of material, processing techniques must
be able to retain the indicator mineral(s) and do so without
contaminating the sample, without losing indicator minerals,
and at a reasonable cost. 
Indicator minerals can be recovered from a variety of sam-
ple media, including stream, alluvial, glacial, beach or eolian
sediments and residual soils. They are also recovered from
weathered and fresh bedrock as well as mineralized float. The
combinations of processing techniques used by exploration
companies or government agencies for recovering indicator
minerals are quite variable (e.g. Gregory & White 1989;
Peuraniemi 1990; Davison 1993; Towie & Seet 1995; Chernet
et al. 1999; McClenaghan et al. 1999). These workshop notes are
a summary of a more detailed paper describing common pro-
cessing methods used to reduce sample weight, concentrate
heavy minerals, and recover indicator minerals (Fig. 1)
(McClenaghan in press). The methods used will depend on the
commodities being sought as well as cost per sample. Most
oxide and silicate indicator minerals are medium to coarse sand
sized (0.25 to 2.0 mm). Thus, concentration techniques that
recover the sand-sized heavy minerals can be used. In contrast,
approximately 90% of gold grains, platinum group minerals
(PGM) and sulphide minerals are silt sized (<0.063 mm), thus
concentration of these indicators requires a preconcentration
technique that includes recovery of the silt- as well as the sand-
sized fractions. 
SAMPLE WEIGHT
The weights of material collected for indicator mineral stud-
ies will depend on the type of surficial sediment collected, the
grain-size characteristics of the sample material, the commod-
ity being sought and shipping costs (Table 1). For example, in
glaciated terrain clay-rich till samples may be as much as 20 to
30 kg (or more) in order to recover a sufficient weight of sand-
sized heavy minerals (Table 2 - #5) (e.g. Spirito et al. 2011).
Coarse-grained silty sand till, typical of shield terrain, requires
smaller (10 to 15 kg) samples because it contains more sand-
sized material in the matrix (Table 2- # 1 to 4) (Spirito et al.
2011). Alluvial sand and gravel samples collected for recovery
of porphyry Cu indicator minerals (PCIM) need only be ~0.5
kg because porphyry Cu alteration systems are large and rich in
indicator minerals (Averill 2007). Bedrock and float samples
usually vary from 1 to 10 kg. 
Overview of processing methods for recovery of 
indicator minerals from sediment and bedrock samples
M. Beth McClenaghan
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada K1A 0E8 
(email: bmcclena@nrcan.gc.ca)
Final concentration
Lithology examination
>2 mm or >1 mm
 Indicator Mineral Identification:
Bulk sediment sample:
10 to 40 kg
 Heavy Fraction:
Ferromagnetic
Separation
 Nonferromagnetic fraction:
Dry sieve to 
specific size fractions
Sieve <2 mm 
or <1mm
Preconcentration
jig, spiral, shaking table, 
Knelson Concentrator,
DMS, or pan
3 kg split for 
geochemical analysis 
& archive 
heavy liquids, and/or
magstream
Magnetic fraction:
Examine or store
2. Chemical analysis: electron 
microprobe, LA-ICP-MS, Ion microprobe
 Indicator mineral 
selection
Store under-/over-
sized fractions
1. Examine & photograph
< 2mm
Fig. 1. Generalized flow sheet showing the steps in sample process-
ing that are used to reduce sample weight, concentrate heavy miner-
als, and recover indicator minerals.
2 M.B. McClenaghan
BEDROCK PREPARATION
Bedrock or float (mineralized boulders) samples often need to
be disaggregated or crushed prior to processing to reduce rock
fragment/mineral grain size to <2 mm. Electric pulse disag-
gregation (EPD) using an electric current from a high-voltage
power source in a water bath is an efficient means of liberating
mineral grains from rock (Cabri et al. 2008). The major advan-
tage of this method is that individual mineral grains can be
recovered in their original shape and form regardless of grain
size. Conventional rock crushers may also be used, however,
they are more difficult to clean between samples and thus pose
a higher risk of cross contamination, often break rock frag-
ments across grain boundaries, and mark/damage grains as
they are liberated. Barren quartz should be disaggregated or
crushed as a blank between routine rock samples to reduce and
monitor contamination. 
PRECONCENTRATION
If sample shipping costs are an issue, samples may be partly
processed in the field to reduce the weight of material shipped
to the processing laboratory. Samples may be sieved to remove
the coarse (>1 or >2 mm) fraction, which may reduce 
weights by a few % to 30% (e.g. Table 2-columns B-C).
Preconcentrating, using a pan, jig, sluice box or Knelson con-
centrator, also may be carried out in the field to further reduce
the weight of material to be shipped. Preconcentrates may be
examined in the field, significantly reducing the time to obtain
results for follow up. However, preconcentraing in the field can
itself be expensive and time consuming and the available meth-
ods may not provide optimal recovery of the indicator miner-
als of interest. Field setup of concentrating equipment may be
more rudimentary than at the processing laboratory, thus extra
care is required to avoid cross contamination or material lost
during the pre-concentration procedure completed in the field.
Whether sieved off in the field or in the laboratory, the
coarse >2 mm fraction may be examined to provide additional
information about sample provenance and transport distance.
The <2 (or <1 mm) fraction is preconcentrated most com-
monly using sieving and/or density methods (e.g. jig, shaking
table, spiral, dense media separator, pan, Knelson concentra-
Target
Typical Sample 
Weight (kg)
Table Micropan Ferro-
magnetic
separation?
Ferro-
magnetic
separation?
A. Sediment Samples
Gold 10 Single Yes 3.3 Yes
Kimberlite 10-30 Double No 3.2 Yes
Massive sulphides
(Ni-Cu-PGE, BHT, VMS,
IOCG, MVT, skarn)
10 Single
Yes
(PGM
only)
3.2 Yes
Porphyry Cu 0.5 No No 2.8, 3.2 Yes
Uranium 10 Single Yes 3.3 Yes
Heavy mineral sands
(grade evaluation) 20 Triple No 3.3 Yes
Tampering
(investigation) Variable Optional Yes 3.3 Yes
B. Rock Samples
Gold, PGE, base metals 1 Optional Yes 3.3 Yes
Kimberlite 1-10 Optional No 3.2 Yes
Tampering
(investigation) 1 No Yes 3.3 Yes
Required Separations
latot:AerutxeTnoitacoL
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thgiew
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stsalC
)gk(
thgiew:C
tupelpmas
ssorca
gnikahs
)gk(elbat
thgiew:D
elbatgnikahs
etartnecnoc
)g(decudorp
thgiew:E
yvaeH
diuqiL
thgiL
)g(noitcarf
thgiew:F
citengam
noitcarf
)g(
-nonthgiew:G
yvaehgam
larenim
)g(etartnecnoc
mm0.2-52.0
9.744.635.4019.51010.210.30.51llitdnasytlistleBiNnospmohT.1
9.810.316.2041.52114.96.50.51llitydnasyrubduS.2
1.822.58.9131.3535.93.28.11llitdnasytlispmacdloGsnimmiT.3
8.530.220.7737.8346.82.18.9llitdnasytlisetilrebmikBelpirT.4
5.116.52.532,10.703,10.564.24.76llityeyalcatreblAnrehtroN.5
Table 1. Examples of variation in sample weight and processing procedures with sample and target type at Overburden Drilling Management
Ltd.’s heavy mineral processing laboratory (Averill & Huneault 2006).
Table 2. Weight of each fraction generated by a combination of tabling and heavy liquid separation to reduce till sample weight, concentrate
heavy minerals, and recover indicator minerals: A) initial sample weight; B) sieving off <2 mm; C) & D) tabling; E) heavy liquid separation; 
F) magnetic separation; G) final heavy mineral concentrate weight. Till samples are from 1) the South Pit of the Thompson Ni Mine, Thompson,
Manitoba; 2) Broken Hammer Cu-PGE deposit, Sudbury, Ontario; 3) PamourMine, Timmins, Ontario; 4) Triple B kimberlite, Lake Timiskaming
field, Ontario; and 5) Buffalo Head Hills, northern Alberta. 
3Overview of processing methods for recovery of indicator minerals from sediment and bedrock samples
tor) to reduce the weight of material to be examined without
losing indicator minerals. Some of the more common precon-
centration techniques are described below.
Panning
Panning is the oldest method used to recover indicator miner-
als, primarily for gold and PGM. Sediment is placed in a pan
and shaken sideways in circular motion while being held just
under water; heavy minerals sink to the pan bottom and light
minerals rise and spill out over the top (Silva 1986; English et
al. 1987; Ballantyne & Harris 1997). Pans are of various shapes
(flat bottomed or conical) and sizes, and can be made out of
plastic, metal or wood. The advantages of this technique
include that it can be a field or laboratory-based operation, is
inexpensive in terms of equipment costs, and if used in the
field it reduces sample shipping weight and thus cost. Panning
is often used in combination with other preconcentration
methods to recover silt-sized precious metal grains (e.g. Grant
et al. 1991; Leake et al. 1991, 1998; Ballantyne & Harris 1997;
Wierchowiec 2002). The disadvantages of this method are that
it is slow, is highly dependent on the experience and skill of the
operator and therefore requires consistent personnel to per-
form the panning. It is considered to be a rough concentrating
method when used in the field and is followed up with further
laboratory-based concentration techniques (Stendal &
Theobald 1994).
Tabling 
Preconcentration using a shaking (Wilfley) table is one of the
oldest methods for concentrating and separating heavy miner-
als on the basis of density. It recovers silt- to coarse sand-sized
heavy minerals for a broad spectrum of commodities includ-
ing diamonds, precious and base metals, and uranium (Averill
& Huneault 2006). A brief description of the method is sum-
marized below from Sivamohan & Forssberg (1985), Stewart
(1986), and Silva (1986). 
The table consists of a deck covered with up to 1 cm high
riffles covering over half the surface. A motor mounted on one
end drives a small arm that shakes the table along its length. A
slurry of <2.0 mm sample material is put across a shaking table
to prepare a preconcentrate. If kimberlite indicators are tar-
geted, the sample is tabled twice to ensure higher recovery of
the key lower density minerals (Cr-diopside and forsteritic
olivine) and the coarsest grains. The advantages of this method
are its moderate cost, ability to recover indicator minerals for a
broad spectrum of commodities, and ability to recover silt- as
well as sand-sized indicators. It is a well established method for
the recovery of precious metal mineral grains as well as kim-
berlite indicator minerals (e.g. English et al. 1987; McClenaghan
et al. 1998; 2004). The disadvantages of this method include
the loss of some coarse heavy minerals during tabling, the
longer time required to process each sample, and that the
tabling procedure is dependent on the skill of the operator.
Dense Media Separator
A gravity method used to preconcentrate kimberlite indicator
minerals is the micro-scale dense media separator (DMS). An
overview of this method is summarized below from
Baumgartner (2006). 
Heavy mineral concentration is carried out using a gravity-
fed high-pressure cyclone. The <1 mm fraction of a sample is
mixed with fine-grained ferrosilicon (FeSi) to produce a slurry
that has a controlled density. The slurry is fed into a cyclone
where the grains travel radially and helically, forcing the heav-
ier particles toward the wall of the cyclone and the lighter par-
ticles toward the centre. The lighter and heavier particles exit
the cyclone through different holes, with the light fraction dis-
carded and the heavy fraction collected on a 0.25 or 0.3 mm
screen. The heavy mineral concentrate is collected on a 0.25
mm screen and is then dried and screened to remove residual
FeSi. A Tromp curve is used to define the efficiency and preci-
sion of the DMS separation. The DMS is calibrated to recover
the common kimberlite indicator minerals that have a specific
gravity (SG) >3.1 : pyrope garnet, chrome-spinel, Mg-ilmenite,
Cr-diopside, forsteritic olivine and diamond. It is tested using
synthetic density tracers before processing samples. The den-
sity settings and cut points are checked once per day. The
advantages of the micro DMS system are that it is fast, less sus-
ceptible to sample contamination than other heavy mineral
concentrating techniques and not operator dependent. The
method, however, is more expensive than other methods
described here and it does not allow for the recovery of silt-
sized precious and base metal indicator minerals.
Knelson concentrator
The Knelson concentrator is a fluidized centrifugal separator
that was originally designed for concentrating gold and plat-
inum from placer and bedrock samples. However, in recent
years it has also been used to recover kimberlite indicator min-
erals from sediment samples (e.g. Chernet et al. 1999; Lehtonen
et al. 2005). The concentrator can handle particle sizes from
>10 microns up to a maximum of 6 mm. The general pro-
cessing procedure is summarized below from the Knelson con-
centrator website (http://www.knelsongravitysolutions.com). 
Briefly, water is introduced into a concentrate cone through
a series of holes in rings on the side of the cone. The sample
slurry is then introduced into the concentrate cone from a tube
at the top. When the slurry reaches the bottom of the cone, it
is forced outward and up the cone wall by centrifugal force
from the spinning cone. The slurry fills each ring on the inside
of the cone wall to capacity to create a concentrating bed. High
specific gravity particles are captured in the rings and retained
in the concentrating cone. At the end of the concentrate cycle,
concentrates are flushed from the cone into the sample collec-
tor. The advantages of the Knelson concentrator are that it is
fast, inexpensive, and can be mobilized to the field to reduce
the weight of material to be shipped to the laboratory.
However, recovery of kimberlite indicator minerals from silt-
poor material, such as esker sand or stream sediments, is diffi-
cult due to the absence of fine-grained material to keep the
slurry in suspension (Chernet et al. 1999). Knelson concentra-
tors are optimal for recovery of gold and PGM.
Spiral concentrator
Heavy minerals can be recovered using a rotary spiral concen-
trator that consists of a flat circular stainless steel bowl with
rubber ribs that spiral inward, a detailed description of which
is reported by Silva (1986). A spiral concentrator is mounted
on a frame so it can be tilted and has a water wash bar extend-
4 M.B. McClenaghan
ing laterally from one side of the bowl to the centre. As the
bowl spins, water is sprayed from the bar and heavy mineral
grains move up and inward along the spirals to the central
opening where they are collected in a container behind bowl.
Water washes light minerals down to the bottom bowl. The
heaviest minerals are recovered first. The advantages of the
spiral concentrator are that it can be field based and thus
reduce sample weight to be shipped, it is inexpensive to acquire
and operate, it is fast if the material is sandy, and it recovers
indicator minerals across a broad size range from silt- to sand-
size grains. The method, however, is dependent on experience
and skill of the operator, the lower density threshold is vari-
able, there is some loss of heavy minerals and the method is
slow if the sample is clay-rich. It is used mainly for gold recov-
ery (e.g. Maurice & Mercier 1986; Silva 1986; Sarala etal. 2009)
but in the past 10 years it also has been used for the recovery
of kimberlite indicator minerals (e.g. Sarala & Peuraniemi
2007).
Jigs
Jigging is one of the oldest gravity concentration methods and
separates heavy minerals based on differential settling veloci-
ties of mineral grains in water (Stendal & Theobald 1994).
Jigging is performed by hand or by mechanically jerking a par-
tially filled screen of material up and down underwater for sev-
eral minutes. While submersed in water, mineral grains separate
through suspension and gravity effects into layers of varying
specific gravity. Heavier grains concentrate on the surface of
the screen, with the heaviest generally concentrated towards
the centre of the screen forming an ‘eye’. Very heavy minerals,
such as ilmenite and magnetite, will be found at the very cen-
tre of the screen and lighter heavy minerals, such as garnet and
pyroxene, will concentrate at the periphery of the eye.
Diamonds tend to concentrate towards the centre despite their
moderate specific gravity (SG 3.51). A spoon is used to remove
the heavy minerals in the eye for more detailed examination.
For optimal recovery, the jig tailings should be re-jigged 2 to 3
times until no eye exists. The method is typically used for
recovery of gold (e.g. Silva 1986) and kimberlite indicator min-
erals (Muggeridge 1995). The advantages of using a jig are that
it can be field based and thus reduce sample weight to be
shipped, is inexpensive to operate, is relatively fast and works
best for fine to coarse sand-sized grains. It is best used in a
fixed, laboratory-based setting with an experienced operator. 
FINAL CONCENTRATION
Heavy liquid separation
A preconcentrate is usually further refined using heavy liquids
of a precise density to further reduce the size of the concen-
trate prior to heavy mineral selection (Table 2-column E).
Heavy liquid separation provides a sharp separation between
heavy (sink) and light minerals (float) at an exact known den-
sity. It is slow and expensive and therefore not economical for
large volumes of sample material, hence the preconcentration
procedures described above that are used to prepare a precon-
centrate before this step (Stendal & Theobald 1994). The most
common heavy liquids used include methylene iodide (MI)
with a SG of 3.3 and tetrabromoethane (TBE) or the low-tox-
icity heavy liquid lithium heteropolytungstates (LST) both with
SG of 2.9. The density required of the heavy liquid will depend
on the indicator minerals being sought. Some laboratories use
a combination of both heavy liquids, separating first using the
lower density heavy liquid at about SG 2.9 to reduce the vol-
ume of material to be further separated at SG 3.2 or 3.3. (e.g.
de Souza 2006; Le Couteur & McLeod 2006; Mircea 2006).
The recovery of kimberlite and magmatic Ni-Cu-PGE indica-
tor minerals requires heavy liquid separation at SG 3.2 using
dilute methylene iodide to include the lowest density indicators
Cr-diopside and forsteritic olivine. Recovery of porphyry Cu
indicator minerals requires separation at SG 2.8 to 3.2 to
recover the mid-density indicators tourmaline (dravite), alunite,
jarosite, and turquoise (Averill 2007). Some indicator minerals,
such as apatite and fluorite, are of intermediate density but are
recovered mainly from the mid-density rather than the heavy
fraction.
Magnetic separation 
Magnetic separation may be used to further refine heavy min-
eral concentrates and reduce concentrate volume for picking of
mineral species with specific magnetic susceptibilities (Towie &
Seet 1995). The most common magnetic separation is splitting
the ferromagnetic from the nonferromagnetic fraction because
the ferromagnetic minerals can comprise a considerable por-
tion of the concentrate (e.g. Table 2-column F). Removing the
ferromagnetic minerals decreases concentrate size prior to
indicator mineral selection and removes any steel contaminants
derived, in most instances, from sampling tools. The ferro-
magnetic fraction may then be (1) set aside, (2) examined to
determine the abundance and mineral chemistry of magnetite
(e.g. Beaudoin et al. 2011), pyrrhotite or magnetic Mg-ilmenite,
as is the case for some kimberlites (e.g. McClenaghan et al.
1998), or (3) analyzed geochemically (e.g. Theobald et al. 1967).
A hand magnet or plunger magnet is most commonly used to
carry out this separation. 
A specific size fraction of the non-ferromagnetic heavy
mineral fraction may be further separated electromagnetically
into fractions with different paramagnetic characteristics to
help reduce the volume of material to be examined for indica-
tor minerals (Averill & Huneault 2006). Minerals such as dia-
mond are nonparamagnetic, pyrope garnet, eclogitic garnet,
Cr-diopside and forsteritic olivine are nonparamagnetic to
weakly paramagnetic, and Cr-spinel and Mg-ilmenite are mod-
erately to strongly paramagnetic (see Table 1 in McClenaghan
& Kjarsgaard 2007). If the non- or paramagnetic portion of
the concentrate contains a significant amount of almandine
garnet it may be processed through a magstream separator to
separate the orange almandine from similar looking eclogitic or
pyrope garnets. Magstream separation divides the concentrate
into (1) a fraction containing most of the silicates (e.g. pyrope
and eclogitic garnet) and no almandine, and (2) a fraction con-
taining ilmenite, chromite and other moderately magnetic min-
erals such as almandine (Baumgartner 2006). 
INDICATOR MINERAL SELECTION 
AND EXAMINATION
The non-ferromagnetic fraction is commonly sieved into two
or three (e.g. 0.25-0.5 mm, 0.5-1.0 mm and 1.0-2.0 mm) size
fractions for picking of indicator minerals, however the final
size range will depend on the commodity sought. For example,
kimberlite indicator minerals are most abundant in the 0.25-0.5
5Overview of processing methods for recovery of indicator minerals from sediment and bedrock samples
mm fraction (McClenaghan & Kjarsgaard 2007) and thus to
maximize recovery and minimize counting time and cost, this
finest size fraction is most commonly picked.
Indicator minerals are selected from non-ferromagnetic
heavy mineral concentrates during a visual scan, in most cases,
of the finer size (e.g. 0.25-0.5 mm, 0.3-0.5 mm or 0.25-0.86
mm) fractions using a binocular microscope. The grains are
counted and a selection of grains are removed from the sam-
ple for analysis using an electron microprobe (EMP) to con-
firm their identification. Methods for examining a sample for
counting/picking vary from rolling conveyor belts to
dishes/paper marked with lines or grids. If a concentrate is
unusually large, then a split is examined and the indicator min-
eral counts are normalized to the total weight of the concen-
trate. If a split is picked, the weight of the split and the total
weight should both be recorded. Not all grains counted in a
sample will be removed for EMP analyses. If this is the case,
the total number of grains counted and the number of grains
removed should both be recorded.
Indicator minerals are visually identified in concentrates on
the basis of colour, crystal habit and surface textures, which
may include features such as kelyphite rims and orange peel
textures on kimberlitic garnets (Garvie 2003; McClenaghan &
Kjarsgaard 2007). Scheelite and zircon in a concentrate may be
counted under short-wave ultraviolet light. Gold and PGM
grains may be panned from concentrates that were prepared in
such a way that the silt-sized fraction has been retained (e.g.
tabling). The grains may be counted and classified with the aid
of optical or scanning electron microscopy. Commonly, gold
grains are classified according to their shape/degree of wear
(e.g. DiLabio 1990, Averill 2001), which can provide informa-
tion about relative transport distances (McClenaghan & Cabriin press).
INDICATOR MINERAL CHEMISTRY
Mineral chemical analysis by EMP, scanning electron micro-
probe (SEM), laser ablation-ICP-MS, or secondary ion mass
spectrometry (SIMS) may be carried out to determine major,
minor and trace element contents of specific indicator miner-
als because mineral chemistry is used to confirm identity,
establish mineral paragenesis, and in some cases deposit grade
(e.g., Ramsden et al. 1999; Belousova et al. 2002; Scott 2003;
Heimann et al. 2005). For example, kimberlite indicator miner-
als are characterized by a specific range of compositions that
reflect their mantle source and diamond grade (e.g. Fipke et al.
1995; Schulze 1997; Grütter et al. 2004; Wyatt et al. 2004). Gold,
PGM and sulphide grains may be analyzed to determine their
trace element chemistry or isotopic compositions (e.g. Grant et
al. 1991; Leake et al. 1998; Chapman et al. 2009). Prior to indi-
cator mineral grains being selected from a heavy mineral con-
centrate, newer techniques such as mineral liberation analysis
(MLA), computer-controlled scanning electron microscopy
(CCSEM), or quantitative evaluation of materials by scanning
electron microscopy (QEMSCAN) may provide quantitative
mineralogical analysis and identification of indicator minerals
in a portion of the heavy mineral concentrate that has been
prepared as a polished epoxy grain mount, in the 0.25 to 2.0
mm fraction of the rarely examined <0.25 mm fraction. These
methods can be used to identify indicator minerals of interest
and prioritize grains for further detailed and more costly EMP
analysis, thus reducing EMP analytical costs. The cost per sam-
ple for these new techniques is, in general, more expensive than
conventional methods. 
QUALITY CONTROL
Project geologists may use a combination of blank samples (no
indicator minerals), spiked samples (known quantity of specific
indicator mineral species), and field duplicates, as well as
repicking of 10% of the heavy mineral concentrates to moni-
tor a laboratory’s potential for sample contamination and qual-
ity of mineral grain selection. In addition, heavy mineral pro-
cessing and identification laboratories can be asked to report
their own quality control monitoring procedures and test
results. Quality assurance and control measures are being
implemented at the Geological Survey of Canada for projects
using indicator minerals (Spirito et al. 2011). 
SUMMARY
These workshop notes describe some of the procedures avail-
able for processing surficial media and rocks to recover indica-
tor minerals for mineral exploration. The processing method
used will depend on sample media, commodities being sought,
budget, bedrock and surficial geology of the survey area, and
processing methods used for previous batches. When report-
ing indicator mineral results in company assessment files, gov-
ernment reports, or scientific papers, it is helpful to report the
laboratory name, processing methods used, and sample
weights. Monitoring of quality control is essential at each stage
in the processing, picking, and analytical procedures described
here and should be monitored both by the processing labora-
tories and clients. Geologists are encouraged to visit process-
ing and picking laboratories so that they have a clear under-
standing of the procedures being used and can discuss cus-
tomizations needed for specific sample batches.
ACLMPW;EDGEMENTS
S. A. Averill of Overburden Drilling Management Ltd., 
T. Nowicki and M. Baumgartner of Mineral Services Canada,
and L. Cabri of CNT-MC are thanked for providing informa-
tion about the procedures used in specific heavy mineral pro-
cessing labs. GSC Contribution No. 20110083.
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Indicator Mineral Methods in Mineral Exploration, Workshop 3, 7-11. 25th International Applied Geochemistry Symposium
Indicator minerals have been successfully used in diamond
exploration for more than 50 years worldwide. Kimberlites
contain a rich mineral inventory that includes olivine, peri-
dotitic and eclogitic garnets, chrome spinel, chrome diopside,
Mg-ilmenite, enstatite, phlogopite, and periclase among others.
Kimberlite indicator minerals (KIMs) for the purposes of this
presentation can be subdivided into two groups: 1) typical or
common and 2) exotic. Common kimberlite indicator minerals
belong to two mantle assemblages – peridotitic and eclogitic
(Stachel & Harris 2008; Gurney et al. 2010). Peridotitic KIMs
include pyrope garnet (of lherzolitic or G9 and harzburigitic-
dunitic or G10 chemical affinity), Mg-rich ilmenite, Cr-rich
spinel, Cr-rich diopside, enstatite, and forsteritic olivine.
Eclogitic indicator minerals primarily consist of eclogitic (Na-
rich) garnet and Na-rich omphacitic clinopyroxene (commonly
with elevated K contents reflecting the high pressures involved
in their formation). Exotic kimberlite minerals include such
phases as corundum and uvarovite (Ca-Cr-rich garnet). 
Corundum is present in kimberlites and as inclusions in dia-
monds but also occurs in peraluminous metamorphic rocks
and peralkaline syenites and pegmatites.Corundum – espe-
cially with elevated Mg, Cr, Ni, Ti, and Fe concentrations – is
an important indicator mineral in kimberlite exploration
because it is most probably derived from eclogite xenoliths fre-
quently carried by kimberlite melts (Hutchinson et al. 2004).
Kimberlite-borne eclogitic xenoliths are commonly associated
with impressive diamond grades - they average 14,000 cpt, fre-
quently up to 90,000 cpt (Spetsius 2004). One eclogitic xeno-
lith (66 grams) from Udahcnaya Pipe in Siberia contains 74
microdiamonds implying grade of 144,000 cpt. 
Uvarovite essentially is a crustal mineral, but when found in
kimberlites is positively correlated with diamond grade of indi-
vidual pipes (as exemplified by several pipes in Siberia and
Canada). Uvarovite is typically associated with chromites and
Cr-rich ore formations including certain skarns, but in the
absence of such rock formations within certain exploration
territory, it can be successfully used – together with other
KIMs – to locate primary diamond sources. 
Another potential “exotic” indicator mineral of kimberlitic
assemblage is moissanite (SiC), which has been documented in
kimberlites and glacial and alluvial sediments from Siberia,
Canada, China, Western Australia, Tersky Bereg of Kola
Peninsula, and Latvia (Hodireva et al. 2003; Shiryaev et al.
2011). Moissanite has also been reported as inclusions in dia-
monds from Fuxian kimberlite in China (Leung 1990). 
Besides chemical and optical identification of kimberlite
indicator minerals, detailed studies of their crystal shape and
other surficial features (such as cleavage, surface sculptures,
formation of secondary alteration production such as
kelyphitic rims on garnets) are of great importance in diamond
exploration, specifically for estimating the mode and distances
of transport of these indicator minerals. The purpose of this
mineralogical exercise ultimately is determination of proximity
of primary magmatic sources of kimberlitic indicator minerals,
which means the ground locations of kimberlitic pipes.
Presence of KIMs with so-called “diamond chemistry” (e.g.
minerals formed under P-T-Of conditions compatible with dia-
mond formation and stabilization in cratonic lithosphere) is
crucial for location of diamond-bearing kimberlite pipes as
opposed to barren diatremes. 
Kimberlitt AS’s exploration in eastern Finnmark established
the presence of olivines and chrome diopsides with diamond
window chemistry as well as corundum, uvarovite, and Mg-
spinel in till, lake, and river sediments. Some diamond window
KIMs in eastern Finnmark show complete preservation of
such crystal features as cleavage, which suggests derivation
from local kimberlite sources (within <1 km). These data are
compared with exploration results from the Arkhangelsk 
diamond province and the Devonian Belt of the Eastern
European Craton (Lithuania, Estonia, Novgorod, and Pskov)
and possible implications for location of diamondiferous kim-
berlitic pipes through regional exploration are discussed. 
EASTERN FINNMARK (NORWAY)
Eastern Finnmark is underlain by thick Precambrian continen-
tal crust which, on the basis of our recent geochronological
studies, reveals complex crustal evolution history. Oldest inher-
ited zircon grains from basement grey gneisses yield Early
Archean ages of 3.69 and 3.2 Ga, suggesting the presence of a
very old crustal component under this part of the East
European craton. The peak of crustal production in Eastern
Finnmark happened around 2.8-2.9 Ga, which was followed by
another episode of thermal re-activation, high-grade metamor-
phism, and granitic magmatism at 2.5 Ga. This crustal chronol-
ogy suggests that Eastern Finnmark retains a protracted his-
tory of evolution of mature continental crust that is broadly
similar to terrains in other Northern Atlantic cratons, such as
Finland, Greenland, and Canada. 
Kimberlitt AS carried a reconnaissance sediment sampling
survey within a part of Eastern Finnmark covering an area
over 3,000 km2. Several populations of indicator minerals have
been subsequently recovered including olivines, chrome diop-
sides, Mg-spinel, corundum, and uvarovite. Olivines have Fo
contents of 86 to 92 and elevated Ni contents of up to 0.6
wt.%, comparable with those typical of kimberlitic olivines
(Kamenetsky et al. 2008). Chrome diopsides display low-Al
(under 1 wt.% of Al2O3) and Cr contents of 1.5 wt.%. Some
clinopyroxenes also have elevated Na concentrations coupled
with high Cr contents, which is typical of mantle-derived diop-
sides. These chrome diopsides from Eastern Finnmark plot
into a field of diamond inclusion clinopyroxenes on a Cr2O3-
Indicator minerals in diamond exploration: A case study from 
eastern Finnmark, Arkhangelsk and the Devonian Belt 
(Estonia, Lithuania, Novgorod, and Pskov)
Pavel Kepezhinskas
Kimberlitt AS, Tolbugatta 24, Oslo, Norway (e-mail: pavel_k7@yahoo.com)
Al2O3 discrimination diagram. Corundum exhibits high Cr,
Fe, Mg, and Ni contents, consistent with their kimberlitic
provenance (Hutchison et al. 2004). So far the regional miner-
alogical signature in Eastern Finnmark is chrome
diopside>olivine>>corundum>Mg-spinel>uvarovite.
However, it is the appearance of the KIM grains that might be
helpful in unlocking the diamond potential of Eastern
Finnmark.
Fairly significant populations (locally up to 20-30 percent of
the total number of heavy minerals recovered from till or river
sediment) of indicator mineral grains from Eastern Finnmark
retain primary magmatic crystal habits and are characterized by
a minimal degree of chemical abrasion and physical wear.
Some chrome diopsides show features such as mineral cleavage
and some forms or sculptures, which are indicative of growth
in igneous melts (Fig. 1), suggest of very limited transport in
fluvio-glacial systems, and possible origin from local kimberlite
sources. Cleavage is a particularly important diagnostic feature
in relation to localization of primary magmatic sources of
these clinopyroxene grains since it can not be preserved in
diopside grains during transport by water or ice over distances
of more than several hundreds of metres. Other chrome diop-
sides exhibit various degrees of chemical abrasion (Fig. 2) that
are indicative of more complicated transport histories and
advanced travel distances. Magnesian spinel shown in Figure 3
has retained its original octahedral crystal shape and magmatic
crystal growth features, which – as in the case of the chrome
diopside grain shown in Figure 1 – is also an indication of its
derivation from local magmatic sources. 
ARKHANGELSK
The Arkhangelsk region of northwest Russia is underlain by
Precambrian continental crust composed of Late Archean to
Proterozoic granulites, gneisses, granites, and greenstone belts
(terrains). Mantle conditions beneath the Arkhangelsk region
are comparable to classic diamondiferous cratons worldwide,
such as the Kaapvaal craton in South Africa and the Slave cra-
ton in Canada. Single clinopyroxene thermobarometry defines
a cool continental geotherm similar to the 36 mW/m2 geot-
herm calculated by Kukkonen et al. (2003) for the 600 million
year old Karelian craton. These mantle conditions are
favourable for diamond formation within the Arkhangelsk
mantle at depths of 110 to 224 kilometres (corresponding to
the diamond stability field) and are further confirmed by geo-
chemical signatures of pyropes and chromites from a high-
grade Arkhangelskaya pipe in the Lomonosov diamond
deposit (Lehtonen et al. 2009). Kostrovitsky et al. (2004) report
pressures of 28 to 68 kbars derived from a megacryst suite
(garnet, clinopyroxene, Mg-ilmenite, phlogopite, and garnet-
pyroxene intergrowths) in the diamondiferous Grib pipe,
which again is supportive of kimberlites sampling diamond-
rich mantle withina cool cratonic keel beneath the
Arkhangelsk region. Low-hematite content of ilmenite
megacrysts suggest low oxygen fugacity and overall reducing
conditions in the mantle during its formation, which indicates
an environment favourable for diamond preservation
(Kostrovitsky et al. 2004). 
Indicator mineral studies in the northern part of the
Arkhangelsk region are abundant and have led in the past to
successful discoveries of more than 30 kimberlite pipes, seven
of which – 6 pipes of Lomonosov kimberlite cluster and the
8 P. Kepezhinskas
Fig. 1. Chrome diopside from Eastern Finnmark with primary mag-
matic features (such as cleavage) indicative of short transport 
distances (Jakobselv Target Area, sample 1083).
Fig. 2. Partially resorbed and chemically altered chrome diopside sug-
gesting a more complex transport history.
Fig. 3. Unabraded Mg-spinel grain retaining primary magmatic 
features.
9
Grib pipe in the Verkhotina kimberlite field – carry economic
diamond mineralization. These pipes include the spectacular
Grib pipe with a net present value of 9.3 billion US dollars in
the ground and a high-grade (0.85 to 1 cpt) Arkhangelskaya
pipe within the Lomonosov kimberlite cluster that is currently
being mined by the Russian diamond producer ALROSA.
The regional study discussed in this presentation is focused
on the central and southern Arkhangelsk region and was car-
ried out in 2006 to 2008 by a now defunct private diamond
explorer, Russian Diamonds plc.
Abundant indicator minerals were collected within the
Tokshenga property in the central Arkhangelsk region (Fig. 4).
Indicator minerals are dominated by pyrope garnets (both G9
and G10 types), olivine (Fo content of 87 to 95, Ni content up
to 0.4 wt.%), chromite, and low-Al, high-Cr clinopyroxene.
Spatial distribution patterns, morphology of individual KIM
grains combined with local ice-flow directions suggest the
presence of kimberlitic sources within the western portion of
this area (Fig. 4). 
Indicator minerals within the southern part of the
Arkhangelsk region (Lachsky property) are dominated by
pyrope garnets. Based on microprobe analyses of more than
70 grains collected from Quaternary river sediments, it appears
that a vast majority of diamond grains have originated within
the diamond stability field (Fig. 5). Co-variation of Cr2O3 and
CaO in these garnets indicates that most of the grains are lher-
zolitic G9 garnets with harzburgitic G10 garnets forming a
subordinate but prominent population (Fig. 5), suggesting that
kimberlite source rocks of these pyropes might be associated
with diamond mineralization. Although some garnet grains
Indicator minerals in diamond exploration: A case study from eastern Finnmark, Arkhangelsk and the Devonian Belt
110 Depth (m) to Target
Pyrope (1-8 grains)
Chromite (1-2 grains)
CPX (1-50 grains)
National Park
Carboniferous
Vendian
N
Ultramafics &
Greenstone Belts
Devonian
KIM Distrubution
Archean
0 30km
Tokshenga License
Quaternary Ice
Direction
Olivine (1-3 grains)
Fig. 4. Distribution of indicator minerals in central part of the Arkhangelsk region (Russian Federation).
Fig. 5. Chemical composition and crystal morphology of indicator minerals in southern part of the Arkhangelsk region (Russian Federation).
show clear signs of chemical abrasion (pitting) and physical
wear (extensive rounding) indicative of large transport dis-
tances, a number of low-Ca pyropes exhibit angular forms
with well preserved elements of original chemical textures,
suggesting that they were derived from local kimberlite
sources. 
THE DEVONIAN BELT – BALTIC STATES
The Baltic States are located within a geological feature known
as the Devonian Belt, which is essentially a significant area
within the western portion of East European Craton domi-
nated by Devonian sedimentary cover. Kimberlite indicator
minerals were reported earlier from Latvia (Hodireva et al.
2003) and were later discovered by us in Lithuania and Estonia
under the auspices of a regional reconnaissance study funded
by De Beers in the early 1990s. 
Indicator minerals were recovered from both Devonian and
Quaternary sediments in Lithuania. KIM populations are
clearly dominated by chrome spinels with subordinate garnets
and minor picroilmenite (chrome spinel>>garnet>Mg-
ilmenite). Chrome spinels form a typical “regional array” on
the Cr2O3-MgO discrimination plot with approximately 10
percent of all chemical analyses (185 analyses) plotting within
or near the diamond inclusion field (Table 1). Garnets are
dominated by lherzolitic compositions; however some border-
line G10 chemistries have been also detected (Table 1).
Magnesian ilmenites are characterized by fairly high MgO con-
tents and are consistent with the overall derivation of
Lithuanian indicator mineral suites from kimberlitic sources.
Indicator minerals from Devonian sedimentary rocks (Skervele
suite) are mostly heavily abraded, suggesting their processing
through one or more secondary sedimentary collectors, while
indicator grains from modern river sediments contain a healthy
population (about 30 percent) of grains showing only minor
chemical alteration or no signs of any significant transport at
all. 
Indicator minerals in Estonia are less abundant compared to
Lithuania, but it also might reflect some sampling bias (less
samples collected in Estonia due to certain time limitations).
Indicator mineral populations in modern river sediments are
dominated by garnets with subordinate spinels. Several grains
of corundum with elevated Ni contents (45-65 ppm) were also
recovered. Garnets are mostly lherzolitic G9 and borderline
G9/G10 varieties. Spinels have moderate to high chrome
chemical compositions with elevated FeO contents and Fe/Mg
ratios. Overall recovered indicator minerals in Estonia were
interpreted as broadly kimberlitic in origin. However, most of
the grains show extensive degrees of chemical abrasion and
nearly total absence of primary magmatic features, which sug-
gests to us that these indicator minerals were probably deliv-
ered into modern river drainage from secondary sedimentary
collectors of Devonian/Carboniferous/Permian and even
possibly Paleogene/Neogene age and reconstruction of their
transport distances and, hence, localization of primary kim-
10 P. Kepezhinskas
garnet garnet garnet ilmenite spinel spinel spinel spinel garnet garnet spinel
SiO2 40.94 40.11 41.2 n.d. n.d. n.d. n.d. n.d. 40.21 41.19 n.d.
TiO2 0.63 0.52 0.26 47.05 0.09 0.0 0.03 0.0 0.3 0.26 0.18
Al2O3 20.55 20.11 20.55 0.22 4.63 7.09 8.43 4.55 19.21 19.22 6.57
C O 4 59 5 16 5 18 1 23 64 98 63 22 61 07 65 17 5 59 4 69 60 9
Oxide
Lithuania Estonia
Cr2O3 4.59 5.16 5.18 1.23 64.98 63.22 61.07 65.17 5.59 4.69 60.9
FeO 7.88 7.17 7.12 42.34 19.5 16.08 19.84 16.53 6.71 7.03 20.97
MnO 0.33 0.23 0.26 0.34 0.36 0.33 0.41 0.36 0.32 0.31 0.42
MgO 20.56 21.21 20.59 8.21 10.01 13.86 9.43 13.79 22.05 22.13 10.25
CaO 4.85 4.55 4.68 n.d. n.d. n.d. n.d. n.d. 4.78 4.46 n.d.
Na2O 0.0 0.05 0.12 n.d. n.d. n.d. n.d. n.d. 0.21 0.12 n.d.
Total 100.33 99.12 99.96 99.39 99.77 100.58 99.21 100.4 99.38 99.41 99.29
Note: n.d. - not determined
Table 1 . Chemical composition of indicator minerals in modern sediments from Lithuania and Estonia.
tenragtenragtenragenexoryponilcenexoryponilcetinemlietinemlietinemlitenragtenragtenrag
OiS 2 .d.n.d.n.d.n71.1477.0436.04 93.55 92.0444.0410.2438.55
OiT 2 28.00.031.00.00.075.4470.4446.848.00.00.0
lA 2O3 35.6124.6121.7119.036.045.095.086.098.6128.6159.41
rC 2O3 10.961.0155.821.142.16.062.015.030.751.880.21
61.665.643.570.125.130.2495.6468.9317.740.761.7OeF
53.04.043.00.00.044.03.0064.084.03.0OnM
97.0282.0216.1294.6132.6196.777.884.887.9148.9110.91OgM
76.594.517.470.5253.52.d.n.d.n.d.n31.673.630.5OaC
aN 2 .d.n.d.n.d.n86.094.0.d.n.d.n.d.n.d.n.d.n.d.nO26.9957.9918.9964.00163.00116.9985.00171.8949.9974.9961.99latoT
denimretedton-.d.n:etoN
edixO
noigervoksPnoigerdorogvoN
Table 2. Chemical composition of indicator minerals in modern sediments from Novgorod and Pskov regions of Russian Federation.
11
berlitic sources in reality represents an unrealistic, if not
impossible, task.
THE DEVONIAN BELT – NOVGOROD AND
PSKOV REGIONS OF RUSSIAN FEDERATION
Indicator minerals were reported in high concentrations (up to
300-500 grains per 20 litre sample) throughout the central
European Russia (Novgorod, Pskov, and Tver regions).
Diamonds – both unabraded cubic crystals and fragments –
were also found in the Novgorod region in association with
kimberlitic garnets and spinels (Table 2). Garnets are mostly
chrome-rich pyropes, some with well developed kelyphitic
rims, suggesting short transport distances and local kimberlitic
sources. Other garnets show variable degrees of chemical abra-
sion, suggesting complex transport history and possible resi-
dence in one or more Paleozoic sedimentary collectors.
Follow-up on several strong pyrope/chrome spinel indicator
trains led to a discovery of a metakimberlite pipe in the central
Novgorod region, however no information on its diamond
content is available at this time.
CONCLUSIONS
The case studies presented above highlight the importance
of regional and local surveys of indicator minerals in diamond
exploration. Local geochemical signatures – predominance of
certain minerals over other indicators – can be established
through such surveys and can be used to characterize individ-
ual kimberlite clusters or larger kimberlite provinces on a cra-
ton scale. Not all traditional kimberlite indicator minerals –
peridotitic and eclogitic garnets, chrome spinels, Mg-ilmenites,
chrome diopsides, forsteritic olivines – should and can be pres-
ent, but the presence of indicator minerals with diamond
inclusion chemistry is essential for ultimate exploration suc-
cess. Some kimberlite provinces, fields, and clusters are associ-
ated with “exotic” indicator minerals, such as corundum (with
elevated Cr, Ni, Fe, and Ti concentrations) and green Ca-Cr
uvarovitic garnet, which can provide valuable information on
the location of primary kimberlitic sources and even provide
some possible insights into the potential diamond grade of
these kimberlitic sources (e.g. uvarovite). Finally, crystallo-
graphic appearance and degree of chemical alteration and
physical wear (degree of rounding, preservation of primary
crystallographic features, cleavage, original magmatic growth
forms on crystal planes, kelyphitic rims on garnets, etc.) of
kimberlite indicator minerals are important in deciphering of
their transport histories, distances from primary sources, and
potential residence in Phanerozoic secondary sedimentary col-
lectors. All these factors are essential in ensuring that each and
every diamond exploration effort leads to ultimate success, not
ultimate failure.
REFERENCES
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Diamonds through time. Economic Geology, 105, 689-712.
HODIREVA, V., KORPECHKOV, D., SAMBURG, N., & SAVVAITOV, A. 2003. Sources
of kimberlitic minerals in clastic sediments of Latvia and some problems
in the succession of formation of supposed kimberlites. Geologija, 42, 3-8.
HOOD, C.T.S. & MCCANDLESS, T.E. 2004. Systematic variation in xenocryst
mineral composition at the province scale, Buffalo Hills kimberlites,
Alberta, Canada. Lithos, 77, 739-747.
HUTCHINSON, M.T., NIXON, P.H. & HARLEY, S.L. 2004. Corundum inclusions
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dataset. Lithos, 77, 273-286.
KAMENETSKY, V.S., KAMENETSKY, M.B., SOBOLEV, A.V., GOLOVIN, A.V.,
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in the Udachnaya-East kimberlite (Yakutia, Russia): types, compositions
and origins. Journal of Petrology, 49, 823-839.
KOSTROVITSKY, S.I., MALKOVETS, V.G., VERICHEV, E.M., GARANIN, V.K. &
SUVOROVA, L.V. 2004. Megacrysts from the Grib kimberlite pipe
(Arkhangelsk Province, Russia). Lithos, 77, 511-523.
KUKKONEN, I.T., KINNUNEN, K.A. & PELTONEN, P. 2003. Mantle xenoliths and
thick lithosphere in the Fennoscandian shield. Physics and Chemistry of the
Earth, 28, 349-360.
LEHTONEN, M.L., O’BRIEN, H.E., PELTONEN, P., KUKKONEN, I.T., USTINOV, V.
& VERZHAK, V. 2009. Mantle xenocrysts from the Arkhangelskaya kim-
berlite (Lomonosov mine, NW Russia: Constraints on the composition
and thermal state of the diamondiferous lithospheric mantle. Lithos, 112,
924-933. 
LEUNG, I.S. 1990. Silicon carbide cluster entrapped in a diamond from Fuxian,
China. American Mineralogist, 75, 1110-1119.
MCCLENAGHAN, M.B., 2005. Indicator mineral methods in mineral explo-
ration. Geochemistry: Exploration, Environment, Analysis, 5, 233-245. 
NIXON, P.H. & HORNUNG, G. 1968. A new chromium garnet end member,
knorringite, from kimberlite. The American Mineralogist, 59, 1833-1840.
SHIRYAEV, A.A., GRIFFIN, W.L. & STOYANOV, E. 2011. Moissanite (SiC) from
kimberlites: polytypes, trace elements, inclusions and speculations on ori-
gin. Lithos, 122, 152-164.
SPETSIUS, Z.V. 2004. Petrology of highly aluminous xenoliths from kimberlites
of Yakutia. Lithos, 77, 525-538.
STACHEL, T. & HARRIS, J.W. 2008. The origin of cratonic diamonds – con-
straints from mineral inclusions. Ore Geology Reviews, 34, 5-32. 
Indicator minerals in diamond exploration: A case study from eastern Finnmark, Arkhangelsk and the Devonian Belt
12
Indicator Mineral Methods in Mineral Exploration, Workshop 3, 13-18. 25th International Applied Geochemistry Symposium
Exploration for the RE and REE and other high-tech metals
(Ga, Ge, In, Li, Nb, Ta, and Ti) is presently active in Finland.
Also, the Geological Survey of Finland (GTK) has launched a
four-year project (2009-2012) to investigate the country’s
potential for high-tech metals. As a part of the project, soil
geochemistry and indicator mineral methods have been used to
trace potential sources for mineralized bedrock. Methodology
used for the exploration high-tech metals is basically the same
as for other commodities, such as base metals, gold, and PGE.
Also, new methods have been developed and tested during the
recent years. 
Till geochemistry is a key method for exploration in
glaciated terrains. A regional till geochemical database and
numerous target-scale datasets collected by GTK are the foun-
dation for estimating the potential for different regions in
Finland. Chemical analyses done using ICP-AES and/or ICP-
MS methods include several elements applicable to high-tech
metal potentiality estimations. For example, elevated concen-
trations of La, Li, Sc, Ti and Y can be used for targeting stud-
ies or for choosing samples for re-analysis with special meth-
ods. New sampling and detailed fieldwork can be done using
test pit surveys and percussion drillings.
RE and REE anomalies in till exist only in ppb or ppm lev-
els, but normally occurring as heavy minerals they can be con-
centrated using gravity separation methods, such as the
Knelson concentrator and heavy liquid. The minerals can be
concentrated further by magnetic separation. The coarse
fractions (>200 μm) can be investigated by hand picking under
optical microscope. However, the microscopic identification of
RE and REE minerals is challenging and requires a lot of man-
ual SEM-EDS (scanning electron microscope + energy disper-
sive spectrometer) work to analyze the selected individual
grains for chemical composition. 
The searching for and analysis of the indicator minerals can
be also automated by using a modern SEM and suitable soft-
ware. One of the most exciting new applications is the fully
automated study of the till fine fraction (<63 μm) mineralogy
by the Mineral LiberationAnalyzer (MLA). The MLA consists
of a modern FEI Quanta 600 SEM, two energy dispersive X-
ray detectors, and JKTech quantitative mineralogy software,
which allow quantitative analysis of mineral and material sam-
ples (Fig. 1). The analyses are done from the monolayer pol-
ished sections of the heavy mineral concentrates. 
In this paper, two case studies from different parts of
Finland are presented to demonstrate the applicability of MLA
to detect RE and REE minerals in soil.
CASE STUDY 1: REVONKYLÄ AREA IN
ILOMANTSI, EASTERN FINLAND
In the Ilomantsi study area (Fig. 2), a pyrochlore anomaly had
been discovered in till during an earlier heavy mineral survey
for diamond indicator minerals (Lehtonen et al. 2009).
Altogether approximately 100 pyrochlore grains were detected
in the 0.25-1.0 mm fractions of three Knelson-concentrated
originally 60 kg basal till samples. The grains were analyzed by
a Cameca SX100 electron microprobe, and compositionally
they could be classified into (1) yttro-betafite-(Y), (2) yttro-
pyrochlore-(Y), and (3-4) uranobetafite varieties (Fig. 3). The
source for the grains remains unknown. Based on the micro-
analytical data, both pegmatitic and alkalic source rocks are
possible. In the context of the GTK high-tech metals project,
additional sampling was carried out in the area.
The sample processing flow sheet is given in Figure 4. For
the traditional indicator mineral work the samples were
processed as in the previous study, using the standard Knelson-
based protocol for diamond indicator minerals (Lehtonen et al.
2005). -63mm sample material was subjected to geochemical
(ICP-AES, ICP-MS) and MLA analyses. For the MLA, the
heavy mineral fractions were concentrated using HMS (heavy
media separation) and LIMS (low-intensity magnetic separa-
tion), followed by mounting in epoxy. The analyses were car-
ried out on polished monolayer mounts, where graphite-pow-
der was used to separate the grains. From each sample 2 to 4
mounts were made, corresponding roughly to 300,000 to
800,000 individual mineral grains. Energy-dispersive X-ray
(EDX) analyses were taken from all heavy mineral grains with
density higher than that of zircon (4.7). The selection was
based on backscatter electron (BSE) imaging. 
Exploring RE and REE mineralization using indicator minerals
M. Lehtonen1, J. Laukkanen2 & P. Sarala3
Geological Survey of Finland
1. P.O. Box 96, FI-02151 Espoo, Finland
2. Tutkijankatu 1, FI-83500 Outokumpu, Finland
3. P.O. Box 77, FI-96101 Rovaniemi, Finland
E-mail jukka.laukkanen@gtk.fi
Fig. 1. The Mineral Liberation Analyzer (MLA). Photo: Geological
Survey of Finland.
The results of geochemical analyses show no anomalous
contents of RE and REE compared to the regional back-
ground. The MLA analyses were carried out on those samples
where pyrochlore grains had been found by hand picking of
the coarser (0.25-0.5 mm) Knelson-concentrated heavy min-
eral fractions, and samples taken adjacent to them. Pyrochlore
was detected in all analyzed samples, 24 grains per sample in
maximum (Table 1). The results correlate well with those by
hand picking, the most enriched samples coincided by both
methods. It can be also estimated, that the number of mineral
grains studied by both methods was roughly in the same order
of magnitude. 
In addition to pyrochlore, the MLA detected other REE-
bearing minerals (columbite-tantalite, monazite, xenotime and
allanite). Many of them were found in even higher concentra-
tions than pyrochlore. By hand picking only monazite was
detected, which was by far the most common REE-bearing
mineral in the sample material. The absence of the other REE-
minerals in the hand-picked concentrates can probably be
explained by their difficult recognition under optical micro-
scope. 
CASE STUDY 2: SAARISELKÄ-PORTTIPAHTA AREA
IN CENTRAL LAPLAND
In the other target selected for this paper, the Saariselkä-
Porttipahta area (Fig. 5), samples collected for gold exploration
had showed anomalously high concentrations of lantanides
(e.g. yttrium and cerium) in till and weathered bedrock, when
compared to the regional background. The aim was to find out
into which minerals the lantanides are bound, and moreover,
the reason for the geochemical anomaly on the northeast side
of Porttipahta. During the exploration, only monazite grains
14 M. Lehtonen, J. Laukkanen & P. Sarala
Fig. 2. The Revonkylä sampling area (1), Ilomantsi, Eastern Finland. The sampling sites are indicated by dots, the arrow shows the main ice-flow
direction in the region. © National Land Survey of Finland licence no MML/VIR/TIPA/217/11. 
Fig. 3. The microanalyses of the Ilomantsi pyrochlore grains shown
in the compositional classification diagram by Hogarth (1977). The
numbers 1 to 4 correspond to (1) yttro-betafite-(Y), (2) yttro-
pyrochlore-(Y), and (3-4) uranobetafite. 
15
had been detected in the heavy mineral concentrates of the
originally ~20 kg samples, but no other REE-bearing minerals
had been found. However, in the mobile metal ion (MMI)
studies conducted in the area there were clearly traces of ele-
vated high-tech metal concentrations (Sarala et al. 2008). 
The remaining sample material from the Saariselkä-
Porttipahta area was subjected to further investigation. The
coarser fractions (0.25-1.0 mm) were concentrated by heavy
liquid and studied under binocular microscope and SEM-EDS.
The fine fractions (-63 μm) were analyzed by the MLA using
the same procedure as for the Ilomantsi samples. From each
sample 2 polished mounts were made, corresponding roughly
to 300,000 to 400,000 mounted mineral grains. Interesting
grains identified by the MLA were subsequently analyzed by a
Cameca SX100 electron microprobe. 
No REE-bearing minerals were detected during micro-
scopic work of the coarse fraction, but the MLA investigation
revealed several of them (Table 2). The samples contained
abundant monazite (max. 12,000 grains/sample) and another
mineral (Fig. 6) close in composition to it (max. 20,000
Exploring RE and REE minalization using indicator minerals
Till sample
60kg
Knelson
Concentrator
Dry screen
0.25mm
Grain size
analysis
Wet screen -63μm
Bisection
Geochemical
analysis
HMS d>3.3
LIMS
Wet screen -63μm
Bisection
HMS d>3.3
LIMS
Hand picking
SEM/EDS
EPMA
2 subsamples
MLA analysis
Wet screen -1mm
LIMS
Geochemical
analysis
+0.25mm
-0.25mm
HMS d>3.3
LIMS
MLA analysis
(á 2kg)
Fig. 4. The processing flowsheet for the Ilomantsi till samples. LIMS = low-intensity magnetic separation, HMS = heavy media separation, SEM-
EDS = scanning electron microscope + energy dispersive spectrometer, EPMA = electron probe micro analyzer, MLA = mineral liberation analyzer. 
90hoP_U_62490seK_U_62490niP_U_62490hoP_U_1E62490niP_U_1E624RM71_U624RM01_U624RM60_U624
lareniM tnuoCniarGtnuoCniarGtnuoCniarGtnuoCniarGtnuoCniarGtnuoCniarGtnuoCniarGtnuoCniarG
422142113223)Y(-erolhcoryp-orttY
11serolhcoryp_rehtO
60157512etilatnat_etibmuloC
dloG 11
htumsiB 1
etiyeldeH 13
4211123212etileehcS
529251032361149etirohT
nocriZ *26861*82751
488221623etiyeleddaB
982171315363040279510656401656etizanoM
037211652361415etisantsaB
1856841301401655737emitoneX
72026211etinallA
etilonocriZ 11
111etisomahC
00291779718234105226912764811157latoT
mm0.1-52.0fognikcipdnaH
66008126600)Y(-erolhcoryp-orttY
.tnemerusaemehtnidedulcnisawnocriZ-*
Table 1. The MLA-results of the Ilomantsi heavy mineral concentrates, fraction -63 μm.
grains/sample). This water-containing mineral is more
enriched in Y and Nd and less enriched in Ce compared to
monazite. The mineral was identified as rhabdophane based on
microanalytical data. In addition to monazite and rhabdo-
phane, xenotime was the third Y-bearing mineral in the sam-
ples (max. 2000 grains/sample). 
When crosschecking