Two  different  beach  placer samples from Srikurmum of Andhra Pradesh and Navaladi of  Tamilnadu were collected and characterized in terms of their  total heavy mineral content by heavy media as  well  as  magnetic separation studies. Navaladi beach  placer  sample  contains higher

amounts of total heavy minerals than that of the Srikur-mum beadh. Mineralogical  analysis  on both  the samples revealed high amounts of garnet and  minor quantities of ilmenite. The particle size of garnet is coarser than that of ilmenite. EPMA results  indicated  that  garnet  is of almandine variety. The Eastern  Ghats  metarnotphic  belt, covering both the areas, is considered to be the source of

these beach placer minerals

Bhaskar Raju, G

Prabhakar, S

Rao, D S

Rao, S Subba

Vijaya Kumar, T V

English

eprints@NML

Characterization of Srikunntan and Navaladi Beach Placer Minerals D. S. Rao, T. V. Vijaya Kumar, S. Subba Rao, S. Prabhakarr21 and G. Bhaskar Raju National Metallurgical Laboratory Madras Centre C S I R Madras Complex, Chennai — 600 113 Email: swaprabha@yahoo.com Abstract Two different beach placer samples from Srikurmum of Andhra Pradesh and Navaladi of Tamilnadu were collected and characterized in terms of their total heavy mineral content by heavy media as well as magnetic separation studies. Navaladi beach placer sample contains higher amounts of total heavy minerals than that of the Srikurmum beadh. Mineralogical analysis on both the samples revealed high amounts of garnet and minor quantities of ilmenite. The particle size of garnet is coarser than that of ilmenite. EPMA results indicated that garnet is of almandine variety. The Eastern Ghats metarnotphic belt, covering both the areas, is considered to be the source of these beach placer minerals. 1. Introduction India is endowed with a coastline of over 6000 kilometers along the eastern and western sea boards, covering Gujarat, Maharastra, Goa, Karnataka, Kerala states on the west coast while Tamilnadu, Pondicherry, Andhra Pradesh, Orissa and West Bengal on the east coast. India is blessed with large reserves of strategic and economically important heavy minerals such as ilmenite, rutile, zircon, monazite, garnet and sillimanite along these eastern and western coastal states. Out of these six heavy beach placer minerals, the first four are prescribed as atomic minerals. Depending upon its main end uses these six different minerals are classified into titanium bearing minerals (ilmenite, rutile), abrasive (garnet), refractory (sillimanite) and nuclear (monazite and zircon) minerals. However, the workable deposits are located only around Chatrapur (Orissa): between Vizag-Srilcakulam . (Andhra Pradesh); between Tiruchendur and Kanylcumari (Tarmlnadu) on the east coast and near Chavara (Kerala) on the west coast. These placer deposits are unique due to (i) an assemblage of four to six minerals (or better termed as multi mineral deposits) m different proportions in different areas (ii) completely liberated unlike other ores (iii) heavy minerals with varying magnetic susceptibility and conductivity lend themselves for less expensive physical beneficiation methods in natural state itself (iv) naturally ground and need no grinding and (v) easy mining as these are not compacted, consolidated and cemented. The formation, identification, exploration and exploitation of these heavy mineral deposits are complex than that meets the eyes at the first sight for which one needs detail characterisation studies especially the heavy mineral content. 65 2. Materials And Methods 2.1 Srikurmum coast: The coastal stretch between the Nagavalli and Vamsadhara rivers in the Srikakulam district, Andhra Pradesh which is referred as the Srikurmum coast, extends over 22 kilometers in length (Fig.1) with and average width of about 700m [1]. The general trend of the Srikurmum coast is N 45° E - S 45° W with rock exposures right at the coast. Srikurmum area follows prominent lineaments trending NNW-SSE. The river Vamsadhra joins the Bay of Bengal near kalingapatnam and Nagvalli at Mopasbandar in Srikakulam district. These two small traveled rivers, originating from the Eastern Ghats terrain, and a creek (Lppi Gedda) supply the bulk of the sediments from the hinder land area [2]. 2.2 Navaladi coast: Situated 17 kilometers north of Kudamkulam, the deposit extends N65°E — S65°W over a coastal length of 10 kilometers and with a width of 50 to 200 meters [3]. The Eastern Ghats metamorphic belt (Fig.2), covering both the above areas, forms the prominent hills along the east coast of India, underlain by various rock types metamorphosed to granulite facies, is considered to be the source of these beach placer minerals [4]. BY SS' 	 6 • OD' .• — Z 	 ALVIGAPATNIN 2D 	 WENT OF w® carom 1B• 20•  : ,, • SRD(UliNAM is. BAY 	 Of -: 	 BENGA 	 L 	 r '. 	 IT of 	 CI 	 214 	 II, • v y 54' 	 64° Oa Fig.!: Mineral sand deposit of Srikurmum 	 Fig.2: Map of India showing the extent of coast, A.P. (after All et al., 2001) 	 Eastern Ghats granulite belt (Kamineni et al., 1991). Around 150 kilograms of the beach placer sample was drawn from Srikurmum as well as Navaladi area for their characterization studies. Both the samples were processed for estimation of total heavy mineral (THM) content using Bromoform (CHBr3; specific gravity 2.89) as a media for separation of heavier fractions from the lighter ones. Further the sample was subjected to magnetic separation (using Permroll of 20,000 Gauss) for obtaining magnetic and non-magnetic fractions. The bulk sample was classified using ASTM sieves. After sieving each sieve fraction was again subjected to magnetic and heavy media separation. Petromineralogical studies were carried out, by stereomicroscopy as well as LEITZ Orthoplan optical microscope, to decipher the heavy mineral content. Some of the heavy minerals were analysed with the help of a JEOL EPMA Super Probe JXA — 8600 model, with an accelerating voltage of 15 kV and a specimen current of 2x10-8 A and 66 using SPI mineral standards. Particle size analysis was carried out using a laser diffraction particle size analyzer (CILAS 1180, France) and also by standard sieves. 3. Results and Discussion 3.1 Classification: Sieve analysis of the Srikurmum ROM sample indicates that most of the material is distributed between -420 to 105 microns while Navaladi ROM sample distributed between -600 to 105 microns. 3.2 Magnetic separation: Magnetic separation studies of the ROM sample of Srikurmum, have shown 26.76% of magnetic minerals (Table 1) while the magnetic separation of the individual sieve fractions have indicated 27.50% of total magnetic minerals (Table 2). The magnetic separation of the sieve shows that the magnetic minerals are enriched slowly from coarse to fine (-600 microns to -105 microns). Similarly magnetic separation studies of the ROM sample of Navaladi area have indicated 33.22% of magnetic minerals (Table 1) while the magnetic separation of the individual sieve fractions indicated 33.15% of total magnetic minerals (Table 5). Table 1: Magnetic and heavy media separation of ROM sample of Srikurmum and Navaladi Area Magnetic separation Heavy media separation Magnetic % Non-magnetic % Heavy % Light % Navaladi 33.22 66.78 34.20 65.80 Srikurmum 26.76 73.24 29.96 70.04 3.3 Heavy media separation: Heavy media separation studies of the ROM sample from Srikurmum have indicated that the sample contains around 29.96% of total heavy minerals (Table 1). However, slightly higher percentage (32.95%) of heavy minerals was obtained by the heavy media separation studies of the individual sieve fractions (Table 2). Similar phenomena were observed in case of Navaladi (Table 1 and 3). The higher amount of heavy minerals in due to the sillimanite and zircon content, which are not reported in the magnetic fractions due to their non-magnetic nature. Table 2: Distribution of minerals in various sieve fractions of Srikurmum beach placer sample Size distribution of the ROM sample Distribution of magnetic and non-magnetic minerals in sieve fractions Distribution of heavy and light minerals in sieve fractions Sieves (u) % Distribution Mag. % Non-Mag % Heavies % Lights % +1700 0.12 Magnetic separation was not carried out as the sample fraction was very less (0.71%). Heavy media separation was not carried out as the sample faction was very less (0.71%). -1700+850 0.06 -850+600 0.53 -600+420 2.84 0.470 2.585 0.75 4.11 -420+300 25.59 2.350 23.267 1.78 38.93 -300+210 31.64 3.760 27.027 1.66 10.25 -210+150 21.68 6.816 15.511 7.48 8.65 -150+105 11.97 8.461 3.995 13.29 4.78 -105 5.57 5.640 0.118 7.99 0.33 Total 100.00 27.497 72.503 32.95 67.05 67 Table 3: Distribution of minerals in various sieve fractions of Navaladi placer sample Size distribution of the ROM sample Distribution of magnetic and non-magnetic minerals in sieve fractions Distribution of heavy and 	 1 light minerals in sieve fractions Sieves (R) % Distribution Mag % Non-Mag % Heavies % Lights % +1700 0.06 Not done Not done -1700+850 0.60 0.03 0.52 0.13 3.05 -850+600 5.00 0.62 3.64 1.97 11.67 -600+420 10.95 2.63 7.98 3.74 11.80 -420+300 39.21 9.35 28.81 3.29 9.77 -300+210 24.56 9.00 18.07 6.03 9.49 -210+150 14.34 7.78 6.33 10.23 10.97 -150+105 4.31 3.07 1.27 9.28 3.34 -105 0.97 0.67 0.23 1.96 3.28 Total 100.00 33.15 66.85 36.63 63.37 3.4 Characterisation: The sand, from the above two beaches, comprises gravel, silty sand and medium to coarse sand followed by fine sand. The heavy minerals that are economically important associated with these beach placer sands are ilmenite, and garnet in substantial quantities and sillimanite and zircon as traces. The non-economical minerals are quartz, feldspar, hypersthene, diopside, augite, sphene, hornblende and tourmaline. Ilmenite occurs mostly as subrounded to subangular grains with moderate relief, marked by numerous surface pits. Micromoiphological features noticed on the ilmenite grains include mainly itch features and signs of mechanical impact. Leucoxene and anatase occur as patches along margins, fractures and within ilmenite due to alteration. In rare instances, ilmenite was seen completely altered to anatase/leucoxene. The garnet occurs as angular to subangular grain occasionally subrounded grains and is characterized by conchoidal fracture. Common appearance of sillimanite is in the form of prismatic crystals sometimes as needle shaped crystals. Magnetic as well heavy media separated heavy fractions were characterized microscopically, for both Srikurmum as well as Navaladi samples, for their mineral distribution and presented in the Tables 4a and 4b and Table 5 respectively. In both the samples, it was observed that the ilmenite content increases while garnet content decreases with fineness (Figs.3-4). Table 4a: Mineralogy of magnetic portion of Srikurmum beach placer Sieve classified fractions Minerals of the magnetic fractions Garnet % Ilmenite % *Others % -600+420 p. 90.98 4.77 4.25 -420+300 p. 91.76 5.26 2.98 -300+210 R 90.22 7.75 2.03 -210+150 p 87.54 10.65 1.81 -150+105 p 72.70 26.12 1.18 -105 1.t 53.37 46.10 0.53 *Others = unliberated opaques associated with garnet and other silicates l'ke quartz, feldspar and sillimanite 68 Table 4b: Mineralogy of the heavy fraction of Srikurmum beach placer Sieve classified fractions Minerals of the heavy fractions Garnet % Sillimanite % Zircon % Ilmenite % Others % -600+420 p. 77.20 10.13 1.17 6.51 4.99 -420+300 p. 78.15 10.43 0.56 7.49 3.37 -300+210 p. 80.56 9.02 0.60 8.42 1.40 -210+150 p. 78.56 10.57 0.47 9.37 1.03 -150+105 4 65.67 8.25 0.62 24.54 0.92 -105 p. 40.33 7.87 0.89 49.78 1.13 Fig.3: Srikurmum beach placers. (a) Distribution of heavy minerals in the heavy fraction Garnet (G), Sillimanite (S) and opaques (0); (b) Distribution of heavy minerals in the light fraction feldspar (f) and quartz (Q); (c) Distribution of heavy minerals in the heavy fraction Zircon (Z) grains (d) Distribution of heavy minerals in the non-magnetic fraction. 69 Table 5: Distribution of minerals in the Navaladi beach placer sample Sample ID Garnet % Rmenite % Others % ROM sample 22.3 11.8 65.9 Magnetic separation of classified fractions ROM Magnetic 62.5 28.4 9.1 Non-magnetic 0.6 1.2 98.2 -850+600 p Magnetic 82.3 0.7 17 Non-magnetic - - 100 -600+420 p. Magnetic 91.8 0.9 7.3 Non-magnetic 0.5 - 99.5 -420+300g Magnetic 83.9 6.0 10.1 Non-magnetic 0.4 - 99.6 -300+210 p magnetic 79.6 11.6 8.8 Non-magnetic 0.4 - 99.6 -210+150 p. Magnetic 69.4 21.8 8.8 Non-magnetic 0.5 1.9 97.6 -150+105 p. Magnetic 46.9 41.1 12.0 Non-magnetic 1.5 6.0 92.5 -105 p. Magnetic 47.9 42.8 9.3 Non-magnetic 1.6 6.5 91.9 Heavy media separation of classified fractions -850+600 p. Heavy 87.5 0.6 11.8 Light - 100 -600+420 p. Heavy 94.5 0.9 4.6 Light 0.4 - 00.6 -420+300 p. Heavy 84.6 4.5 10.9 Light 0.5 0.02 99.3 -300+210 p. Heavy 63.3 10.3 26.4 Light 0.4 - 99.6 -210+150 p. Heavy 65.2 20.8 14.0 Light 0.5 0.5 99.0 -150+105 p. Heavy 41.7 45.2 13.1 Light  Heavy -  25.5 -  60.7 100 13.8 -105 p. Light - - 100 Table 6: EPMA data of Srikurmum placer minerals (wt%) Garnet Garnet Ilmenite Sillimanite Si02 39.187 40.388 --- 37.454 A1203  18.884 12.372 0.651 61.832 FeO 3.880 15.582 48.404 0.194 MgO - 8.940 1.213 -- Mn0 1.961 0.211 1.002 CaO 33.351 11.288 0.003 - 1C20 ---- 1.733 --- --- Na20 ---- 1.900 0.044 TiO2 0.104 2.644 49.151 0.025 Cr203 0.146 0.066 0.214 ZnO 0.028 0.118 0.018 = not detected 70 Fig.4: Distribution of ilmenite with reference to the fineness of the material of Navaladi sample (black grains are ilmenite) 3.5 Electron probe microanalysis: Ilmenite is the dominant member of the heavy mineral assemblage and as such declares the commercial prospect of any beach placer deposit because of wide variety of end uses. Some of the heavy minerals were analysed by Electron Probe Micro-analyser (Table 6 and Table 7) to decipher their mineral chemistry. The ilmenite from Srikurmum area contains 48.404% FeO and 49.151% TiO2 with minor amounts of MgO and MnO while chromium, aluminium, calcium and zinc in traces. The ilmenite from Navaladi area contains 45.218% FeO and 51.624% TiO2 with minor amounts of MgO and MnO while chromium, aluminium, calcium and zinc in traces. Magnesium and manganese in ilmenite are due to substitution for Fe2+. The presence of significant amounts of magnesium and manganese indicates that the ilmenite of both the areas constitute a solid solution series with geikielite and pyrophanite respectively. As a result of this solid solution, the TiO2 content of these ilmenites is lower than the ideal value (52.65%). 71 Cumulative  value  (%)  100 80 40 20 60 -o- Head sample -0- Mag fraction -s- Nonmag fraction -0-- Nonmag -0- Mag -A- Head Table 7: EPMA data of Navaladi placer sample (wt%) Garnet Garnet Garnet Garnet Ilmenite Si02 39.454 38.468 38.115 38.783 A1203 20.677 20.621 20.647 19.831 0.614 FeO 29.578 33.056 30.540 29.969 45.218 MgO 7.605 4.357 6.017 6.943 1.862 MnO 0.357 1.011 0.622 0.514 0.801 CaO 0.811 1.287 1.840 1.474 0.391 Na20 0.047 0.049 TiO2 0.052 0.064 0.049 0.066 51.624 Cr203  0.031 0.087 0.132 0.127 0.162 ZnO 0.122 0.049 0.038 0.026 V205  0.280 = not detected 3.6 Particle size distribution: Particle size distribution of the ROM sample as well as magnetic and non-magnetic products, from Srikurmum area, (Fig.5) clearly shows that the magnetic fraction is higher in particle size than that of the non-magnetic portion. Particle size distribution of the ROM sample as well as magnetic and non-magnetic products, from Navaladi area, (Fig.6) also shows a similar trend. 0 200 400 600 800 1000 Particle size (microns) Fig.5: Particle size distribution of the Srikurmum ROM sample along with its magnetic as well as non-magnetic fraction 0 200 400 600 800 1000 1200 Particle size (microns) Fig.6: Particle size analysis of Navaladi ROM sample along with magnetic and non-magnetic fractions 72 4. Conclusions The following conclusions are drawn from the preliminary characterisation study on these beach placer minerals 1. Both Srikurmum and Navaladi placer samples indicated presence of garnet and ilmenite as economically exploitable heavy minerals. 2. The Srikurmum and Navaladi beach placers mostly contain high amounts garnet and minor amount of ilmenite with traces of sillimanite and zircon. The garnet and ilmenite (which are magnetic) show higher particle size range than that of the non-magnetic products. Among garnet and ilmenite the particle size of garnet is coarser than that of the ilmenite. 3. Navaladi beach placers contain higher amounts of total heavy minerals than the Srikurmum beach placer minerals. 4. The presence of significant amounts of magnesium and manganese in ilmenite indicates that the ilmenite of both the areas constitute a solid solution series with geikielite and pyrophanite respectively. As a result of this solid solution, the TiO2 content of these ilmenites is lower than the ideal value (52.65%). 5. The Eastern Ghats metamorphic belt, covering both the above areas, forms the prominent hills along the east coast of India, underlain by various rock types metamorphosed to granulite facies, is considered to be the source of these beach placer minerals. 5. Acknowledgements The authors are very much thankful to the Director, NML, Jamshedpur for his encouragement and permission to publish the results. 6. References 1. Ali, M.A., Krishnan, S. and Banerjee, D.C. (2001) Beach and Inland heavy mineral sand investigations and deposits in India — An overview. Exploration and Research for atomic Minerals, vol.13, pp.1-21. 2. Ravi, G.S. , Rao, R.G. and Rao, A.Y. (2001) Coastal heavy mineral sand deposits of Andhra Pradesh. Exploration and Research for atomic Minerals, vol.13, pp.53-83. 3. Chandrasekharan, S. and Murugan, C. (2001) Heavy minerals in the beach and the coastal red sands (Teris) of Tamilnadu. Exploration and Research for atomic Minerals, vol.13, pp.87-109. 4. Kamineni, D.C., Rao, A.T. and Bonardi, M. (1991) The geochemistry of monazite types from the Eastern Ghats granulite terrain, India. Mineralogy and Petrology, vol. 45, pp.190-130. 73 

Characterization of Srikurmum and Navaladi Beach Placer Minerals

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Characterization of Srikurmum and Navaladi Beach Placer Minerals

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