Journal of Minerals & Materials Characterization & Engineering, Vol. 8, No.2, pp 149-159, 2009
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Recovery of Ilmenite and Other Heavy Minerals
from Teri Sands (Red Sands) of Tamil Nadu, India
N. Babu1, N. Vasumathi2 and R. Bhima Rao2*
1National Institute for Interdisciplinary Science and Technology (CSIR),
Trivandrum – 695019, India
2Institute of Minerals and Materials Technology (CSIR)
Bhubaneswar 751 013, India
The red sand which is known as Teri sand in Tamil Nadu consists of 5.5% Total Heavy
Minerals (THM) out of which 3.7% is ilmenite. The other min e r a l s, zircon, sillimanite and garnet
are in the order of abundance identified. On processing this feed to recover ilmenite by using
spirals followed by dry high intensity magnetic separator and high tension separator, the
ilmenite concentrate obtained contains 99.1% ilmenite with 3.5% yield and 94% recovery. The
other heavy minerals, including zircon (53.3%) and sillimanite (31.7%), could be further
processed for recovery of individual mineral of zircon and sillimanite by judicious combination
of gravity and flotation processes.
KEY WORDS: Teri sand, ilmenite, zircon, sillimanite, spiral concentration, high tension
separation, tabling, total heavy minerals.
Inland red Teri sands of southeast India have formed from weathering in situ of coastal dune
sands. The term Teri, which means red, is derived from Tamil, a regional language in south
India. Teri sands are very lean placer deposits for heavy mineral concentration. The beach and in
land placer deposits exhibit a considerable variation in mineralogy and chemical composition
150 N. Babu, N. Vasumathi and R. Bhima Rao Vol.8, No.2
depending on the location. The flowsheets for their beneficiation are therefore variable in detail.
The literature reveals[1-10] that lot of research work carried out on Teri sands but most of the
publications restricted to resource evaluation, geology, geochemistry, mineralogy etc. The
general practice to recover Total Heavy Minerals from such a lean beach sand deposit containing
2-5% THMs is first concentrated to 20 –30% THMs on cone concentrators. This product is then
fed to spirals, which gave a concentrate of more than 80% THMs.
In India the highest concentration of Total Heavy Minerals (THM) in beach sand is found in the
Chavara deposit (70 –80% THM with 60% TiO2) and Manavalakurichi (60 –80% THM with
50% TiO2). Pre-concentration by wet methods is generally not required for these deposits. With
the Orissa deposits (~ 20% THM with ~ 48% TiO2) and for most other deposits throughout the
world, bulk concentration of THMs are needed before actual separation of individual minerals is
carried out. In general, the red sands of Orissa and Andhrapradesh coasts contain on an average
4% to 10% heavy minerals. Ilmenite constitutes around 60 -75% among heavies. Garnet is
almost negligible amount. Sillimanite is about 5%. Zircon, monazite and rutile constitute around
10%. The rest is pyriboles (hypersthene and augite are common minerals; staurolite and kyanite
are less common minerals). The beach placers and inland 'Teri' sands of Tamil Nadu containing,
principally, ilmenite, rutile, leucoxene, zircon, monazite, garnet, sillimanite, amphibole,
pyroxene and magnetite are classified into three distinct mineralogical provinces based on the
predominance of: (i) ilmenite, (ii) garnet, and (iii) mixed ilmenite - garnet. Mineral assemblages
in 'Teri' sands directly reflect composition of the bed rocks. The average grade of Teri sands of
Tamil Nadu, are about 10% with a total heavy mineral reserves of 96 MT and an ilmenite
reserves of 77 MT (grade of ilmenite 6% in raw soil).
In spite the inland deposits have a complex mineral assemblage compared to the beach washings
and the heavy minerals are finer in size moreover the major gangue mineral quartz is of wider
size range and the content of fine quartz is relatively higher in the inland deposits, it is essential
to process such inland deposits as over the years, the quality of beach washings has come down
drastically. The limited availability of these seasonal accruals has forced the future beach sand
mineral industry to depend on the inland beach deposits as the primary source of feed material.
In view of this, an attempt is made to recover valuable minerals such as ilmenite, zircon and
sillimanite from Teri sands of Tamil Nadu.
2. MATERIALS AND METHODS
Representative raw placer samples were collected from the Teri sands of Tamil Nadu for
beneficiation studies. Samples were processed in order to estimate and separate THM from the
bulk sand of red sand. Petro-mineralogical studies were carried out using a Leica petrological
optical microscope, to identify the components of the total heavy mineral content. Powdered
feed, magnetic and non-magnetic sink were subjected to X-ray diffraction (XRD) using
Vol.8, No.2 Recovery of Ilmenite and Other Heavy Minerals 151
PANalytical (X’pert) powder diffractometer, (scan speed - 1.2°/min from 6° to 40°, by Mo Kα
radiation) to identify the mineral phases in the corresponding fractions. Magnetic and non-
magnetic fractions of heavy minerals were observed using scanning electron microscope (SEM)
for morphological studies. The grains were mounted on a SEM brass stub. The mounted quartz
grains were coated with gold in a vacuum evaporator while the sample was being slowly rotated.
Usually 15-20 grains were studied in detail and typical micrographs were taken by using JEOL
JSM-5800 scanning electron microscope.
Initially the samples were subjected to spiral separation to recover heavy minerals. Concentrate
and tailings were collected from spiral separation and the weight percentages were recorded.
Further, the samples were subjected to magnetic separation using Permroll (14,000 Gauss) to
separate magnetic and non-magnetic fractions and the representative weight percentages were
recorded. The magnetic fraction was subjected to Carpco high tension separator (laboratory
model, drum type) to recover conducting minerals (ilmenite and rutile). The non magnetic
fraction was subjected to Denver gravity table for recovery of heavy minerals such as zircon,
The above samples were processed for the estimation of total heavy mineral (THM) content
using Bromoform (CHBr3; specific gravity 2.89), as a medium for separation of heavier fractions
from the lighter. Methylene iodide (di-ido methane, 3.3 sp.gr.,) heavy medium was used to
determine very heavy minerals and light heavy minerals from the total heavy minerals obtained
by using bromoform heavy medium.
3. RESULTS AND DISCUSSION
3.1 Physical Properties of Teri Sand
Physical properties of the Teri sand of Tamil Nadu area are summarized in Table 1. Bulk density
of the Teri sands are 1.45 g/cc and the true density is 2.89 g/cc. Angle of repose for the same is
30.3 degree. Passing size of the d80 particle size is 360 μm. The total heavy minerals present in
the as received samples are 5.5% by weight, in which the very heavy minerals (>3.3 sp. gr.,) are
4.8% by weight and the light heavy minerals (<3.3 sp.gr.,) are 0.7% by weight. The magnetic
minerals (TMM) are 3.9% by weight. The light mineral (<2.89 sp. gr.,) is the quartz and has
94.5% by weight in the feed. Particle size distribution of the feed (Teri sand sample) as well as
total heavy minerals from Teri sand of Tamil Nadu area, (Table 2 and Figure 1) shows that most
of the feed (as received) samples has particle size distribution between -500 +100 μm size range.
The size of the total heavy minerals falls in the group of finer fractions predominately -300 +50
μm size range.
152 N. Babu, N. Vasumathi and R. Bhima Rao Vol.8, No.2
Table. 1. Physical properties of Teri sand sample (as received sample).
Bulk density, g/cc 1.45
True density, g/cc 2.89
Porosity, % 49.8
Angle of repose, degree 30.3
d80 passing size , µm 360
Moisture content, % 0.5
-50 µm , Wt % 4.7
Total Heavy Minerals (THM), Wt., % 5.5
Total Magnetic Minerals (TMM), Wt., % 3.9
Very Heavy Minerals (VHM), Wt., % 4.8
Light Heavy Minerals (LHM), Wt., % 0.7
Quartz, Wt., % 94.5
Table. 2. Size analysis of teri sand sample and total heavy minerals (as received sample)
Size in µm As received sample Total heavy minerals in as
Wt., % Cum., % passingWt., %Cum., % passing
-1000 + 600 1.7 100.0 0.3 100.0
-600 + 420 7.7 98.3 0.5 99.7
-420 + 300 26.1 90.6 2.2 99.2
-300 + 210 22.9 64.5 17.8 97.0
-210 + 150 11.6 41.6 22.1 79.2
-150 + 100 22.0 30.0 27.4 57.1
-100 + 50 3.3 8.0 20.5 29.7
-50 4.7 4.7 9.2 9.2
Total 100.0 100.0
d80 passing size , µm 360 210
Mineralogy of the Teri sands determined by XRD, petrological optical microscope and scanning
electron microscope are shown in Figs. 2 - 5.
3.3 Microscopic and SEM Studies
Teri sands of Tamil Nadu have been subjected to microscopic studies before and after the
beneficiation studies. The feed samples are shown predominantly of quartz minerals followed by
ilmenite, sillimanite and zircon. Whereas ilmenite, zircon, sillimanite and garnet were the order
identified after the beneficiation techniques (Table 3) and (Figs. 3 - 5). The ilmenite occurs
Vol.8, No.2 Recovery of Ilmenite and Other Heavy Minerals 153
mostly as rounded to semi-rounded grains (Fig. 3). Well developed elongated zircon with out-
growth nature was observed (Fig. 4) in the red sand of Tamil Nadu. The out-growth nature might
have formed during re-crystallization of the sediments. The garnet grains (Fig. 4) were found to
be angular to subangular with occasional subrounded grains and are characterized by conchoidal
Table. 3. Mineralogical composition of teri sand sample (as received sample) and total heavy
mineral distribution in sink.
Minerals Feed, % Sink, %
Ilmenite 3.7 67.5
Zircon 0.9 15.6
Sillimanite 0.7 12.3
Quartz 94.5 0
Total 100.0 100.0
154 N. Babu, N. Vasumathi and R. Bhima Rao Vol.8, No.2
Vol.8, No.2 Recovery of Ilmenite and Other Heavy Minerals 155
SEM studies reveals that the ilmenite marked by numerous surface pits, etch marks, irregular
blocks and solution pits (Fig. 5) were created by mechanical abrasion and chemical processes.
The grain may belong to paleo-sediments and might have been brought to the beach environment
due to reworking of bottom sediments. Very often, zircon is present as well developed crystals
(Fig. 5). Sillimanite shows concodial blockage due to mechanical weathering during
transportation. Well rounded monazite with pitted nature (Figs. 4 & 5) was observed. The grain
might have undergone surface chemical activity and reworking of sediments under favorable
3.4 Recovery of Ilmenite and Other Heavy Minerals
Results of spiral separation on recovery of total heavy minerals (THM) such as ilmenite, zircon,
sillimanite etc., from feed sample are given in Table 4. The data indicate that the concentrate
obtained contain 19.2% by weight. The distribution of THM is 5.2% by weight and the overall
recovery is 95%. The THM loss in tailings is 0.3% and hence it can be rejected. The spiral
concentrate was subjected to dry high intensity magnetic separation (DHIMS) to recover total
magnetic minerals (mostly ilmenite). The data are given in Table 5. The total magnetics obtained
by DHIMS is 19.8% by weight and 98.7% sink. The overall weight distribution is 3.8% and
THM distribution is 19.5% with overall recovery 68%. The magnetic fraction of DHIM is further
subjected to high tension separator (HTS) to recover total ilmenite. The data are given in Table 6.
The total conducting fraction obtained contains 92% by weight and 99.4% sink. The overall
distribution of weight is 3.5% and the THM distribution is 91.5% with overall recovery 63%.
156 N. Babu, N. Vasumathi and R. Bhima Rao Vol.8, No.2
Table. 4. Results of spiral separation
Details Weight, % Sink, % THM, % Rec., %
Concentrate 19.2 27.1 5.2 95
Tailing 80.8 0.4 0.3 5
Total 100.0 5.5 5.5 100.0
Table. 5. Results of Dry High Intensity Magnetic Separator (DHIMS) on spiral concentrate
Details Weight, % Weight
Sink, % THM, % Over all
Magnetic 19.8 3.8 98.7 19.5 68
Non-Magnetic 80.2 5.4 9.4 7.6 27
Total 100.0 19.2 27.1 27.1 95
Vol.8, No.2 Recovery of Ilmenite and Other Heavy Minerals 157
Table. 6. Results of High Tension Separator (HTS) on DHIMS magnetic fraction (Table 5)
Details Weight, % Weight
Sink, % THM, % Over all
Conducting 92.1 3.5 99.4 91.5 63
7.9 0.3 90.5 7.2 5
Total 100.0 3.8 98.7 98.7 68
The non magnetic fraction of DHIMS subjected to gravity table and the results are given in Table
7. The data indicate that gravity table concentrate (mostly zircon and sillimanite) obtained
contain 9.7% by weight and the sink is 93.9%. The overall weight distribution is 1.5% and the
THM distribution is 9.1% with overall 26% recovery. The gravity table tailings contain 0.3%
sink and 0.3%THM and hence this can be rejected.
Table. 7. Results of tabling studies on DHIMS non magnetic fraction (Table 5)
Details Weight, % Weight
Sink, % THM, % Over all
Concentrate 9.7 1.5 93.9 9.1 26
Tailing 90.3 13.9 0.3 0.3 01
Total 100.0 15.4 9.4 9.4 27
Results on recovery of ilmenite and distribution of other heavy minerals in different products
obtained by magnetic, electrostatic and gravity separators are given in Table 8. The data indicate
that by using DHIMS about 97% ilmenite could be recovered and by cleaning this product using
HTS, 99.1% ilmenite could be recovered. Gravity table heavies contain 53.3% zircon, 31.7%
sillimanite and with other impurities can be further subjected to recover individual concentrates
of zircon and sillimanite.
The conceptual flow sheet with material balance on recovery of ilmenite and other heavy
minerals like zircon and sillimanite is shown in Fig. 6. The feed contain 5.5% THM out of which
3.7% ilmenite. On processing this feed through spirals followed by DHIMS and HTS, a
concentrate obtained contain 99.1% ilmenite with 3.5% yield and 94% recovery. The gravity
table concentrate associated majorly with zircon (53.3%), sillimanite (31.7%) and other heavy
minerals which can be reprocessed for recovery of individual mineral concentrates of zircon and
sillimanite by judicious combination of gravity and flotation processes.
158 N. Babu, N. Vasumathi and R. Bhima Rao Vol.8, No.2
Table. 8. Recovery of Ilmenite and distribution of heavy minerals in different products obtained
by magnetic, electro static and gravity separators
Minerals Mags., of DHIMS Conducts of HTS Heavies of Table
Ilmenite 97.0 99.1 5.3
Quartz 1.3 0.6 6.1
Total 100.0 100.0 100.0
The red sand which is known as Teri sand in Tamil Nadu consists of 5.5% Total Heavy Minerals
(THM) out of which 3.7% is ilmenite. On processing this feed to recover ilmenite by using
Vol.8, No.2 Recovery of Ilmenite and Other Heavy Minerals 159
spirals followed by dry high intensity magnetic separator and high tension separator, ilmenite
concentrate obtained contain 99.1% ilmenite with 3.5% yield and 94% recovery. The other heavy
minerals zircon (53.3%) and sillimanite (31.7%) could be further reprocessed for recovery of
individual mineral concentrates of zircon and sillimanite by judicious combination of gravity and
The authors are thankful to the Director of National Institute for Interdisciplinary Science
and Technology (CSIR), Trivandrum and also to the Director of Institute of Minerals and
Materials Technology (CSIR), Bhubaneswar for constant encouragement to carry out this work
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