COMPARATIVE STUDIES on the BLACK SAND CONCENTRATES of SOUTH INDIA by Dr

Home , Black sand

COMPARATIVE STUDIES ON THE BLACK SAND CONCENTRATES OF SOUTH INDIA BY Dr. E. A. V. PRASAD [Department oJ Geology, Sri Venkateswara University, Tirupati (A.P.), Indic]

Received June 24, 1971 (Communicated by Dr. K. Neelakantam, F.A.SC.)

ABSTRACT Samples of the littoral and alluvial placer deposits of the black sand concentrates which contain radioactive resistate minerals were collected from various parts of South India and their characters with respect to colour, density and radioactivity were presented.

With the aid of a hand magnet and a sensitive Frantz Isodynamic laboratory model Lj magnetic separator, each sample was subdivided into magnetic, paramagnetic and nonmagnetic components. The paramagnetic mineral assemblage was further subdivided into fractions of varying mass magnetic susceptibility. The amounts of these fractions constitute the frequency distribution of mass magnetic susceptibility, expressed in terms of current strength, of the sample whose character is ttien evaluated by means of certain standard statistical parameters.

Variation in the characters with respect to grain size was also studied. Fm'ther, it is suggested that the amount of magnetite is an "Index of Maturity" for these residual deposits.

THE voluminous black sand concentrates occurring along the East and West coasts of India, in a series of local concentrations, at favourable localities, constitute a thorium asset of world importance. These placer deposits contain the radioactive mineral, monazite, together with the other industrial minerals ilmenite, garnet, rutile, zircon, magnetite and leucoxene in varying proportions. Such placer deposits of radioactive resistate minerals have been reported from many parts of the world (Nininger,1954; United Nations, 1956; Heinrich, 1958). In India these deposits extend with interruptions from Cape Comorin through Kerala and Maharashtra upto Gujarat as far north as the Narmada Estuary near Broach on the West Coast, while on 231 2 32 E.A.V. PRASAD

the East Coast they extend through Madras and Andhra upto Orissa State. The distribution of these littoral deposits has been given by Tipper (1914), Nininger (1954), Wadia (1956), and Heinrich (1958). Hess (1937) has indicated the alluvial type, containing monazite, extending on the East Coast as far north as Mahanadi river as well as the Krishna river alluvium. Changes in land level and intricate stream diversions are believed to be responsible for the localisation of some deposits of this type (Gillson, 1949). The earlier investigations (Mahadevan and Srirama Das, 1948, 1954; Mahadevan and Sathapathi, 1948 ; Nateswara Rao, 1949 ; Anjaneyulu ; 1950 ; Balasankaram, 1951 ; Rangachari, 1952 ; Mahadevan and Poorna- chandra Rao, 1953; Srirama Das, 1951; La Fond and Prasada Rao, 1954; Mahadevan, 1954; Borreswara Rao and La Fond, 1956; Subba Rao, 1967) were carried out on these black sands occurring in and around the Waltair beach dealing, in general, with their origin and economic importance. David- son (1956) discussed the origin of the Kerala deposits. Borreswara Rao (1957) has carried out a survey of the East Coast extending from Vasishta- Godavary river .in the South to Vamsadara river in the North with special reference to the beach configuration and accumulation of the black sand concentrates. Prasad (1968) worked out the distribution of radioactivity in different size fractions of the black sand concentrates, and Prasad and Naidu (1971) discussed the leaching patterns in zircon and monazite of these deposits. In general, these deposits apparently appear to be of uniform character but actually they exhibit diversity, as the quantity and variety of these resis- tates are functions of: (1) The nature of the source rocks from which they were derived; (2) The nature and intensity of weathering in the source area; (3) The distance and duration of transportation; and, (4) The nature and extent of reworking at the site of deposition. Hence an attempt has been made to present the overall picture of these deposits of both littoral and alluvial environments by means of certain reliable and reproducible methods. The samples of littoral placer deposits were collected (Fig. 1) from Wal- tair (W), Andhra Pradesh; Rameswaram (RM), Cape Comorin (CC), Manavalakurichi (MK) and Muttom (MM) of Madras State; Kovalam (KV) near Trivandrum, Chavara (CH) near Quilon and Varkala (VK) of Kerala Black Sand Concentrates of South India 233

State, and Ratnagiri (RG) and Poornagad (P) of Maharashtra State; the samples of alluvial black sand concentrates were collected from the banks of river Krishna (K) at Vijayawada and the river Sabari (S) at Kunavaram and at the confluence of the rivers Godavary and Vasishta (GV) two miles north of Antharvedi--all in Andhra Pradesh.

FIG. | ?2 ° 76" 80" 84" 8fl* I II 24'

20" 20"

16" 16"

12 ° L ARABIAN SEA k / g~Y OF BE'NG~A~,~ 12'

100 SO 0 100 200

8* 8* iNDIAN OCEAN II ...... ~ -J ,I t 7½, 7~ o 80" 84" 88'

FIG. 1. Outline map cf Scuth India showing location of the sample stations: (1) Waltoir; (2) Rameswaram; (3) Cape Comerin ; (4) Manavalakurichi ; (5) Muttom ; (6) Kovalam; 7) Varkata; (8) Chavara; (9) Ratnaglri; (10) Poornagad; (11) Godavari and Vasishta- confluence; (12) Krishna; (13) Sabari. The [Deccan trap format,cn is indicated by the dotted area.

As the name implies these deposits, in general, are black ; but from Rame- swaram to Cape Comorin the colour is widely varied with all transitions between black and red. At certain places on this part of the coastline the deposits are red, garnet forming the bulk with a little admixture of quartz and having very coarse texture. At Ratnagiri and Poornagad--as a matter of B3 234 E.A.V. PRASAD

fact along the northern part of the West Coast adjoining the Deccan trap terrain, the deposits are fine grained and look dark brown. The deposits in all other localities of the country are dominantly made up of black opaque minerals in which garnet, monazite and zircon are generally recognisable even with the naked eye. Further, within the same sample, the colour very strikingly varies with grain size. As the grain size decreases, there is a progressive diminution of the blackness due to the impoverishment of the dark opaque minerals, particularly limenite, and enrichment of the light coloured transparent minerals, particularly monazite and zircon. In general beyond 120 sieve mesh the blackness disappears and looks yellowish. The den- sities of the samples were determined by the gravimetric method (Tickell, 1965) and the values are given in Tables I and II.

TABLE I

Variation with graht size in a sample of the black sand concentate from Kovolam beach

SI. Grain size Density Magnetic character /3-zctivity No. gm/cm3 CPM/gm M PM NM

1. -- 60 4- 72 sieve mesh; 210-250 microns .. 2.463 0.73 89-18 10.09 202

2. -- 72 4- 100 sieve mesh; 150-210 microns .. 2.653 0.88 72.13 26.99 332 3. -- 100 4- 120 sieve mesh; 125-150 microns .. 2.669 0.94 70.57 28.49 1,911 4. -- 120 4- 150 sieve mesh; 105-125 microns .. 2.920 0.39 60.84 38.77 3,539

MAGNETIC CHARACTER

Each sample, passed through 60 sieve mesh and retained in 150 sieve mesh, was made free of the contaminated quartz by bromoform separation. Then it was washed first with acetone and then with distilled water and dried. Black Sand Concentrates of South India 235

TABLE II Some properties of the black sand concentrates of India

Magnetic character S1. Sample Density p,-activity No. gm/cm 8 M PM NM CPM/gm

1. Waltair .. +2-694 1.31 91.03 7.66 154 2. Rameswaram~I .. +3.050 1-55 93-27 5.18 35 3. Rameswaram--II .. +2.533 2.46 94.94 2.60 33 4. Cape Comorin .. +2.882 0-69 79.75 19-56 1,160 5. Manavalakurichi--I +2.896 0.79 83.37 15.84 468 6. Manavalakurichi--II +2.617 1.32 89.64 9.04 188 7. Muttom .. +2.650 1.05 91.65 7.30 2,600 8. Kovalam .. +2-563 0.81 82.07 17.12 547 9. Varkala .. +2.607 0.96 77.22 21.82 453 10. Chavara .. +2.382 0-67 58.66 40.67 179 11. Ratnagiri .. + 1.934 53.18 46.82 Tr Nil 12. Poornagad .. +1.975 61.38 38.62 Tr Nil 13. Godavari-Vasishta eonttuence .. +2.440 15-03 75.59 9.38 830 14. Krishna .. +2.155 39-02 56-24 4-74 34 15. Sabari .. +2.377 3-91 81.22 14.87 42

Initially, the magnetic portion of each sample, weighing about 30-40 grams, was extracted with hand magnet and its weight was determined. Then the sample was repeatedly passed through a highly sensitive Frantz isodynamic laboratory model L1 magnetic separator and was subdivided into fractions of different mass magnetic susceptibilities by varying the current strength at a constant angle of side slope.

Each sample was run through the magnetic separator, initially applying a current strength of 0-2 ampere and keeping the side slope at 10 °. The magnetic portion separated at this current strength was removed and the rest was again passed through the separator raising the current strength to 0.4 ampere. Thus the sample was repeatedly passed through the separator successively raising the current strength irt steps of 0.2 ampere upto 1.4 amperes at constant set up of the side slope at 10 °. Separation was not 236 E.A.V. PRASAD

made beyond 1.4 amperes as saturation sets in (Flinter, 1959). The weights of the materials separated at each current strength were determined. All these fractions together constitute the paramagnetic mineral assemblage. The weight of the material, non-magnetic at 1-4 amperes, was also determined. In. this set up of the separator, zircon, being diamagnetic, remains in the nonmagnetic poltion. The weight percentages of the three components-magnetic (M), paramagnetic (PM) and nonmagnetic (NM)--for each sample were recalculated (Tables I and II). The composition of any sample can be represented in terms of these three components by a point on a tri- angular diagram. The scatter of the plots for the samples, under study, are shown in Fig. 2.

Eliminating the magnetic and non-magnetic portions, the weight percentages of the fractions corresponding to each current strength were

M 20_;/10 -91 \ 7 ,MM,,o,E\ -k s0.7:,_,...... s0 60-4C ,o.,o/

80 / .,, .A,0.E a

~7--:,...... ~;~~-,;~ ;~----...... - --~°.'°

90-10 $0-20 ?0-30 60-40 50-50 40-60 30-70 20-80 10-90

FIG. 2. Composition of the black sand concentrates. The plots with open circles represent the variation with grain sizz of a sample of the Kovalam beach. Their numbers represent size grades given in Table I. The numbers for all other plots are those of the samples given in Table I1. The subaivision of the fi~'ld illustrates the classification of the black sand concentrates based on the degree of maturity with reference to the magnetite content. Black Sand Concentrates of South India 237 recalculated (Table III). In other words, these data provide the frequency distribution of the mass magnetic susceptibility, expressed in terms of current strength, for the paramagnetic mineral assemblage of a given sample. The data thus obtained was processed in the same way as in the study of the size frequency distribution of a sediment and application of certain standard statistical parameters for evaluating the characters of the black sand concentrates. The statistical parameters for these frequency distributions were

TABLE III Frequency distributions of the mass magnetic susceptibility of the paramagnetic mineral assemblage in the bl,~ck sand concentrates in terms of current strength in ampere~

Current strength in amperes S1. Name of No. the sample 0.2 0.4 0-6 0.8 1.0 1.2 1.4

1. W .. 41-81 49.48 5.95 1.76 0-26 0.12 0-12 2. RM--I .. 45.09 52-10 1-96 0.43 0.21 0-08 0-13 3. RM--II .. 45-31 52-60 0-91 0-30 0-82 0-03 0-03 4. CC ., 29-51 60.53 3.02 5-89 0.84 0-97 0,12 5. MK--I .. 23.15 64.50 6-86 4.41 0.52 0-31 0.25 6. MK--II .. 12.55 60.35 13.20 11-69 1-36 0-37 0-48 7. MM ., 44-57 24.66 12-47 17-57 0-54 0.11 0.08 8, KV .. 25-73 60-35 5.82 6,44 1-36 0-17 0.12 9. VK .. 18.65 62.85 9.20 7.41 0.99 0-60 0-30 10. CH .. 14-81 69.00 10.76 3.56 0.67 0.67 0.53 11. RG .. 39.71 42.38 16.04 0.92 0.25 0-17 0.17 12. P .. 26.25 57.44 15.06 0.77 0.24 0-12 0.12 13. GV .. 35.41 50-82 3.93 6.00 2.54 0.76 0-54 14. K .. 13-54 64-84 14-71 4-44 1-03 0.48 0-96 15. S .. 51.86 41.68 3.76 1.42 0.92 0-18 0-18 calculated from certain critical points of current strength in amperes on their respective cumulative frequency curves. The statistical parameters calculated were Median, Trask's (1932) formula x/Q1/Qz for the Index of Dispersion, Skewness, Kurtosis and Folk's (1962) Standard Deviation. The attributes of the frequency distributions in terms of these statistical parameters are presented in Tables IV and V, 238 E.A.V. PRASAD

~- z ~ ee Black Sand Concentrates of South India 239

TABLE V Attributes of the frequency 4istribution of mass magnetic susceptibility of the paramagnetic mineral assemblage of the black sand concentrates of India

S1. Sample MD D~ SK SD K No.

° W ° ° 0.41 1.213 1.011 0.1306 0.242 2. RM--I .. 0.40 1.163 0.977 0-1073 0.214 3. RM---II .. 0.41 1-193 0-923 0.1075 0.233 4. CC .. 0.48 1.203 0.907 0-1494 0-252

. MK--I 0-49 1-134 0-945 0-1201 0.167 6. MK~II 0.55 1.158 0.979 0.1790 0.160 7. MM 0.43 1.479 1-212 0-2531 0.312 8. KV 0.47 1.188 0.971 0.1545 0-186 9. VK 0.47 1.131 1.071 0.1630 0.130 10. CH 0.47 1.131 1.071 0.0260 0.174 11. RG 0-43 1.272 1.011 0.1570 0-256 12. P 0.48 1.177 0.914 0-1192 0.161 13. GV 0-46 1.225 0.960 0-2131 0.170 14. K 0.54 1-117 0-925 0.1676 0-144 15. S 0-40 1.266 0.900 0.1332 0.286

The fractions separated at each current strength were examined under the microscope. The general nature of these fractions, for all the samples separated at 10 ° side slope, is as follows:

0.2 Ampere.--The material separated at this current strength shows wide variation between 12-52~ by weight. Microscopic examination of this fraction revealed that it is entirely made up of ilmenite. 0.4 Ampere.--24-70% by weight of material was separated. It is entirely made up of ilmenite and garnet. 0"6 Ampere.--1-16% by weight was separated. It is made up of ilmenite and garnet; and monazite may commence to make its appearance. After 0.6 ampere the blackness of the sample disappears with more or less 240 E.A.V. PRASAD

complete elimination of the dark and opaque minerals particularly ilmenite. The remaining portion is somewhat white and the only opaque or semi- opaque mineral present is rutile which is sparsely distributed as small black specks. 0.8 Ampere.---0"5-18% by weight was separated. Except in Ratnagiri and Poornagad samples, 70-90~/o by number percentage of monazite includes in this fraction. Leucoxene makes its presence felt by its contrasted colour of light brown along with the more abundant lemon yellow monazite. 1"0 Ampere.--0.2-1.4% by weight was separated. Monazite and leucoxene continue to be separated. 1.2 and 1.4 Amperes.--O'l-1 "0 by weight percentage was separated Pure ilmenite separated at 0-2 ampere while leucoxene separates from 0.8 ampere onwards upto 1.2 amperes. In between the current strengths of 0-2-1-2 ampeIes this titanium mineral displays widely varying degrees of alteration; in other words, the alteration of ilmenite into leucoxene is accompanied by progressive decrease in its magnetic susceptibility. The most important radioactive mineral, monazite, makes its appearance at 0"6 ampere but bulk of the mineral is found separated at 0"8 ampere; it may continue separation in minor amounts upto 1.2 amperes. From 1 "0 to 1.4 amperes very minor amounts separated and contain monazite, leucoxene, magnetic futile and zircon with microscopic (and sub microscopic ?) inclusions of magnetic materials. The non-magnetic portion ranging from 0-41 by weight per cent is made up mostly of zircon and some amount (5-20 by number percentage) of rutile. Other minerals make up less than 2 by number per cent and includes such minerals as kyanite, corundum, beryl and a few unidentified minerals.

RADIOACTIVITY Each sample which is free from magnetite was finely powdered and exactly one gram of the material was weighed and taken in an aluminium planchet. The /3-activity of these samples was determined with a Geiger- Muller counting system of Trombay Electronics Instruments, India, consisting of Binary Scalar (Type BS : 300), preset timer (Type ET: 450 A), High voltage unit (Type HV; 600), and the Geiger-Muller tube (Type 1:1030)which is of end window type with a wall thickness of 3 rag/era ~ and operating voltage 1,300 V. The B-activity values, expressed in counts per minute per gram (CPM/gm), are given in Tables I and II. Black Sand Concentrates of South India 241

VARIATION WITH GRAIN SIZE The black sand concentrates were formed by mechanical processes in the course of which these resistate minerals were eroded from older rocks, transported by streams and subsequently undergone selective deposition. The fractionation by such mechanical processes will be imperfect and leads to a gradation in grain size and corresponding gradation in chemical and mineralogical composition (Petti John, p. 113, 1957). Variations in the chemical and mineralogical nature with grain size have been discussed by earlier workers (Grout, 1925; Krynine, 1950); such a variation has also been found to be reflected in the distribution of radioactivity (Prasad, 1968). There- fore, the black sand concentrates of the Kovalam beach near Trivandrum were examined with respect to grain size (Table I). In the coarser fractions the minerals of higher mass magnetic susceptibility are more prominently displayed and those of lower mass magnetic susceptibility are insignificant. In the finer fsactions the minerals of higher mass magnetic susceptibility are suppressed while those of lower mass magnetic susceptibility become more prominent. Such mineralogical variation with grain size can be attributed to unequal resistance of different minerals in the assemblage to abrasion. Selective abrasion has resulted in the progressive and systematic elimination of the softer minerals such as ilmenite and garnet and complementary enrichment of the harder and more durable components such as monazite and zircon which is reflected by the progressive increase in the radioactivity and nonmagnetic portion respectively towards the finer sized fractions (Table I). Considering the 'Stability Index' of garnet as unity, those of monazite and zircon have been given the values of 40 and 100 respectively (Dryden and Dryden, 1946). From this it follows that resistance to abrasion incieases with decrease in the mass magnetic susceptibility.

MAGNETITE--A MINERALOGICAL INDEX OF MATURITY One of the major influences on the chemical, mineralogical and textural character of a clastic sediment is 'maturity' the degree to which a sediment has been differentiated or evolved from the parent, materials; in other words, it is a measure of the extent to which it approaches the ultimate end product to which it is driven by the formative processes that operate upon it. Folk (1951) has stated the criteria for the recognition of the different stages of textural maturity. Several indices of compositional maturity have been suggested by earlier workers; but none of them is applicable to the black sand concentrates. Of all their constituents, magnetite is easily susceptible to alteration and destruction. Large amounts of magnetite, present in Ratna- 242 E.A.V. PRASAD girl and Poornagad deposits, are due to the adjoining parent rock, viz., Deccan basalts (Fig. 1) from which the materials were derived and dumped involving very little of transport thereby favouring its preservation. So also less distance of travel accounts for the fairly large amounts of magnetite in the alluvial black sands. Thus they carry a record of the transporting history--its distance and duration, in the amount of magnetite they conlain. It is evident from Table II that the black sand concentrates show a wide range of their magnetite content which reflects their widely varying degrees of residual character and hence of differing degrees of maturity. Based on magnetite content five stages of maturity of the black sand concentrates may be recognised; they are: (1) Immature--50~o; (2) Submature--50--25~o; (3) Mature--25-10~; (4) Overmature--10-3~o; and (5) Supermature--3~o by weight (Fig. 2). The passage from immature to supermature deposits is characterised thus by a progressive decrease in the magnetite content which is achieved rapidly with a progressive increase in the total input of modifying energy imposed in the form of weathering and duration and distance of transport. This may be accompanied by progressive increase in the sorting and rounding of the grains as indicated by Folk (1951) in the case of different stages of textural maturity.

SUMMARY AND CONCLUSIONS

Fifteen samples of the black sand concentrates--twelve from littoral and three from alluvial environments--were examined with respect to their density, radioactivity and magnetic character.

Magnetite is primarily responsible for the blackness of the deposits occurring in the northern part of the West Coast adjacent to the Deccan trap terrain (Ratnagiri and Poornagad), while its contribution to the colour of the alluvial deposits is in varying degrees. On the other hand, the blackness of the littoral deposits in all other parts of the coastline is wholly due to ilmenite.

The characters of the black sand concentrates are evaluated by em- ploying certain standard statistical parameters to the frequency distribution data of mass magnetic susceptibility obtained by repeatedly subjecting the paramagnetic mineral assemblage to separation in the magnetic separator raising the current strength from 0.2 ampere to 1.4 amperes, in regular steps, keeping the side slope constant at 10 °. Black Sand Concentrates of South India 243

For comparison of the black sand concentrates the following indices are suggested:

Fraction Index

1. Magnetic component .. Magnetite content and the degree of maturity. 2. Frequency at 0.2 ampere .. Ilmenite content 3. Frequency at 0.4 ampere •. Ilmenite and garnet 4. Frequency at 0.8 ampere •. Monazite content 5. Nonmagnetic component .. Zircon content

These indices can be used for comparison but do not directly serve for the exact estimation of the mineral content. Further these indices (except the index of maturity) hold good for separation conducted at 10 ° side slope of the magnetic separator. Studies of the grain size variation revealed that the coarser fractions are characterised by the dominance of the minerals of higher mass magnetic susceptibility (ilmenite and garnet) and in the finer fractions they are progres- sively suppressed while the minerals of lower mass magnetic susceptibility (monazite and zircon) are enriched because resistance to abrasion increases with decrease in the mass magnetic susceptibility.

ACKNOWLEDGEMENTS

The financial assistance offered by the University Grants Commission, New Delhi, for this research project is gratefully acknowledged• Thanks are due to Prof. M. G. C. Naidu for providing the necessary facilities for this work, to Mr. G. S~dhakar Rao, Research Scholar, Department of Botany, for kindly drawing the figures and to Mrs. E. Krishna Kumari for her assistance.

REFERENCES

1. Anjaneyulu, B. J. N. S. R. "The study of the black sand concentrates and geology of the coastal strip from Anakapalli to Vizagapatam," Unpub- lished M.Sc. Thesis, Andhra University, Waltair, 1950. 2. Balasankaram, C. .. "The study of the black sand concentrates of the coastal areas of Vizagapatam District from Pudimadaka to Polavaram," Unpublished M.Sc. Thesis, Andhra University, Waltair, 1957, 244 E. A.V. PRASAD

3. Borreswara Rao, C. .. "Beach erosion and concentration of heavy mineral sands," Jour. Sediment. Petrol, 1957, 27, 143-47. 4. ---- andLaFond, E.C. "Study of the deposition of heavy mineral sands at the con- fluences of some rivers along the east coast of India," Andhra University Memoirs in Oceanography, 1958, 2, 48-60.

5. Davidson, C.F. .. "The economic geology of thorium," Mir.eral Mag., 1956, 94, 197-208• 6. Dryaen, L. and Dryden, C. "Comparative rates of weathering of some common heavy minerals," Jour. Sediment. Petrol., 1946, 16, 91-96. 7. Flinter, B.H. .. "The magnetic separation of some alluvial minerals in Malaya," Amer. Mineralogist, 1959, 44, 738-51.

8. Folk, R.L. .. "Stages of textural maturity of sedimentary rocks," Jour. Sediment. Petrol., 1951, 21, 127-30. 9. .. "Sorting in some carbonate beaches of Mexico," Trans. N.Y. Acad. Sci., 1962, 25, 222-44. 10. Gilson, J. L. .. Titanium: Industrial Mineral and Rocks, Am. Inst. Mining Engrs., 1949, pp. 1042-73. 11. Grout, F. F. .. "Relation of tcxturc and composition of clays,' Bull. Geol. Soc. Amer., 1925, 36, 398-416. 12. Heinrich, E. Win. .. Mineralogy and Geology of Radioactive Raw Materials, Mc- Graw-Hill Book Co., Inc., New York, 1958, pp. 654. 13. Hess, F. L. •. "Industrial Minerals' and Rocks, Am. Inst. Min. Met. Eng., New York 1937, pp. 525. 14. Krynine, P. D. •. "Petrology, stratigraphy and origin of the Triassic sedimentary rocks of Conn.," Conn. Geol. and Nat. Hist. Surv. Bull., 1950, pp. 239. 15. La Fond, E. C. and "Beach erosion cycles near Waltair on Bay of Bengal," Prasada Rao, R. Andhra University Memoirs in Oceanography, 1954, 1, 63-77. 16. Mahadevan, C. .. "Some recent results on oceanographic research at the Andhra University," Proc. Pan Indian Ocean. Sci. Congr., Perth, Section F, 1954, pp. 56-63. 17. ~ and Sathapathi, N. "Home of monazite," Curt. Sci., 1948, 17, 297. 18. -- and Srirama "Monazite in the beach sands of Visakhapatnam District," Das, A. Proc. Ind. Acad. Sci., 1948, 27, 275-78. 19. .. "Effect of high waves on the formation of coastal black deposits," Andhra University Memoirs" in Oceanography, 1954, 2, 57-62. 20. Nateswara Rao, B. .. "The study of the beach sands of Vizagapatam District from Rishikonda to Bhimilipatam," Unpublished M.Sc. Thesis, Andhra University, Waltair, 1949. 21, Nininger, R. D. .. Minerals /or Atomic Energy, D. Van Nostrand Co., Inc. Princeton, N.J., 1954, p. 367. Black Sand Concentrates of South India 245

22. Petti John, F.J. .. S.'_liq~e,ttary Rock,, 2nd Ed., Harper and Brothers, New York, 1957, p. 718. 23. Prasad, E A.V. .. ~'On Black sand concentrates," Curr. Sci., 1968, 37, 232. 24. ----and Naidu, M. G.C. "Leaching patterns of monazite and zircon," ibid., 1971, 40, 14-15. 25. Rangachary, A.C. .. "The study of the black sand concentrates along the coast from Bhimilipatam to Kandivalasa river confluence," Un- published M.Sc. Thesis, Andhra University, Waltair, 1952. 26. Srirama Das, A. .. "The black sand concentrates of Visakhapamam beach," Quart. Jour. Geol. Min. Met. Soc. Ind., 1951, 23, 169-80. 27. Subba Rao, H. .. "Studies on the Kakinada Bay on the East Coast of India," Ibid., 1967, 39, 75-91. 28. Tickell, F. G. .. Developments in Sedimentology. 4. The Techniques of Sedi- mentary Mineralogy, Elsevier Publishing Company, I965, pp. 220. 29. Tipper, G. H. .. "The monazite sands of Travancore, "Geol. 7urv. India, Records, 1914. 44. 30. Trask, P.D. .. Origin and Environment of Source Sediments of Petroleumi, Gulf. Publ. Co., Houston, Texas, 1932, pp. 323. 31. United Nations .. Proe. Intern. Conf. Peaceful Uses of Atomic Energy, Geology of Uranium and Thorium 1956, 6, 825. 32. Wadia, D.N. ., "Natural oc~,urrences of uranium and thorium in India," Intern. Conf. Peaeefid Uses of Atomic Energy (Geology of Uraniam and Thorium), United Nations, New York, 1956, 6, 163-66.