ROCK PHOSPHATE IN RAJASTHAN
INTRODUCTION
The term "Rock phosphate" is applied to the rock in which one or more phosphate minerals,
usually calcium phosphate of sufficient grade and suitable composition are present which permits
its use directly or after concentration, in the manufacture of commercial products. The chemical
analysis of rock phosphate is usually reported as a percentage of P 20S or a tricalcium phosphate
Ca3 (P04)2.,
Out of the three major plant nutrients nitrogen, phosphorous and potassium, the phosphrous is
essential for root development, hastening maturity of crops and in increasing the protein content of
grains.
The rock phosphate is an important constituent for the manufacture of the superphosphate, triple
super phosphate, nitro phosphate, mono and diammonium phosphate and dicalcium phosphate
besides other phosphorous based chemicals.
The total reserves of rock phosphate known so far in the country are about 175 million tonnes out
of which 122 M.T. are of low grade containing 10-20% P20S'
In India, rock phosphate is found in the states of Madhya Pradesh (Jhabua), Uttar Pradesh
(Mussoorie)Pithoragarh, Durmula), Himachal Pradesh (Sirmur) Tamilnadu and Rajasthan. Out of
these rock phosphate, only Rajasthan and Madhya Pradesh are of economic importance. ~he rest
all are small deposits of low grade ore. In Madhya Pradesh about 35 million tonnes Rock
phosphate reserves have been assessed containing 20-30% P20S' .
OCCURRENCE IN RAJASTHAN
The Rajasthan deposits are most important from the view point of their P20s content and total
reserves. In the state. The phosphorite deposit ar~ located in Jaisalmer, Udaipur Banswara, Jaipur
and Alwar districts. In Rajasthan it occurs both as rock phosphate and in apatite form.
The description of the deposits in.Rajasthan is given below:
Jaisalmer District
(i) Birmania deposit:
The rock phosphate deposit near Birmania is located about 100 km. northwest of Barmer. It occurs
in the rocks of Palaeozoic age. It can be traced for about 4 kms. in NNE- SSW direction and is'1 to
4 meters thick. The phosphate rock is either calcareous, slaw or sandy in the north but to the south
it occurs as thick black band in limestone. Phosphorite is also associated with cherty bands.
Detailed prospecting which included geological mapping on 1:500 Scale, trenChing and 2054
meters drilling has been carried out and reserve of about 4.34 million tonnes of rock phosphate
with 12.15%P2Os has been estimated in this area.
(ii) Fatehgarh deposit:
The phosphorite horizon occurs about 88 kn\. north of Barmer on Barmer-Jaisalmer road. It can be
traced from Sarda in the east to the small hill, 3 km. S20° E of Bhiyasar, for a distance of 12 km.
The Fatehgarh formation comprises ferruginous sandstone interbedded with yellowish white
friable sandstone and sub bentonitic clays of probably Upper Cretaceous to Eocene age. Its
aggregate thickness is 60-70 metres but the lower 7 to 10 metres only is phosphatic. The grade of
the deposit is quite low.
Udai pur District
Udaipur district is the most important district for phosphate deposits. A large number of
occurrences/ deposits have been located around Udaipur city. The important ones are given below:
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(i) Kanpur deposit:
It is located 8 km. east of Udaipur on Udaipur Jhamarkotra road. The rock formation in the area
belong to the Aravalli Supergroup intruded at places by post- Aravalli granites. The general trend
of the formation is NNE- SSW, dipping at 20°-40° due NNW.
Due to complex folding the phosphate horizon is repeated. The phosphatic material occurs mainly
within light to bluish grey compact limestone or calcareous rocks. The Phosphatic band has a
strike length of about 600 mts. and its thickness varies from 4 to 6 mts. The indicated reserves
have been put at 3.0 million tonnes having 12-13% P205 content. The deposit is being worked by
MI s R.S.M.D.C. Ltd.
(ii) Dakan Kotra
The phosphate deposit is located about 12 km. SSE of Udaipur. The rock formations here are
similar to those found at Kanpur. The rock phosphate occurs within dark grey & bluish limestone
and cherty quartzites. The reserves have been estimated at 1.4 million tonnes having 12 to 20% P
25% content. The deposit is also being worked by M/s. R.S.M.D.C. Ltd.
(iii) Karbaria Ka Guda:
It is situated 1 km. west of Kanpur deposit. The discontinuous horizon of phosphatic rock is 1-5
metres thick. The trend of the rock is N-S which can be seen up to a distance of 1.5 km. In the
northern part rock phosphate occurs at the contact of phyllite and quartzite while in the sourthern
part, it is associated with yellow brown cherty, brecciated quartzite. Its aggregate length is about
300 mts. The reserves have been estimated at 0.5 million tonnes containing 22 to 25% P205.
(iv) Matoon deposit:It is located 15 km. SE of Udaipur City. The rock formations belong to Aravali Supergroup and are
represented by dolomitic marbles, calcareous grits, chert, brecciated quartzite, quartzite & phyllite.
The phosphate band about 1 to 25 mts. thick is traceable for. 3.5 km. length and shows pinching
and swelling but it is usually thick (20m) in cherty quartizite. Based on 25 boreholes covering
2250 mts. drilling the reserve has been estimated to about 9.2 million tonnes.This deposit is being
exploited by Mis Hindustan Zinc Limited
. (v) Sisarma deposit:It is located 10 km. SW of Udaipur and extends over a length of about 2 km. The phosphorite is
associated with cherty dolomitic and siliceous limestone of Aravalli Supergroup having a width of
7-20 metres. 20 channel were cut across the mineralised zone and 11 bore holes with an aggregate
drilling of 492.86 mts. have been drlled in the area. About 0.84 million tonnes of rock phosphate
reserves with 5 to 10% P2O5 up to 50 mts. depth. have been estimated.
(vi) Neemuch Mata deposit:The deposit is located in Kataria hill about 3 km. north-west of Udaipur. The rock formations are
phyllites, shale, dolomite and siliceous limestone of Aravalli Supergroup. The phosphorite
occurs in form of small bends & lenses within 0.75 sq.km. area. On the basis of 32 boreholes
with an aggregate drilling of 1250.45 mts, reserves of 0.11 million tonnes containing 10% P 2°5
and 0.22 million tonnes with 5-10% P2O5 have been estimated in this area.
(vii) Badgaon deposit :The rock phosphate deposit is located about 6 km. north of Udaipur on way to Gogunda. The
rock formations are phyllites, dolomitic and siliceous limestone and quartzite of Aravalli
Supergroup. The rock phosphate occurs in isolated patches, lenses within the limestone. The
width of rock phosphate varies from 3 to 22mt. On the basis of 704.85 mts: drilling spread over
23 boreholes reserves of 3,47,405 tonnes of rock phosphate have been estimated with 3 to
23% P205content. .
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(viii) Jhamarkotra deposit:It is the biggest and high grade phosphorite deposit located about 24 km. SE of Udaipur. The
nearest railway station Kharwa Chanda, is about 10 km. from the deposit and lies on
Udaipurcity-Ahmedabad metergauge section of the western railway. However Umra is the
convenient railway station. The rock phosphate occurs in metasedimentary rocks of Aravalii
Supergroup (Precambrian age). It is of algal origin occuring in benyeen siliceous, ferJ;Uginous,
and cherty dolomitic limestone resting over basal quartzite and gritty quartzite which
unconformably rest over the Banded Gneissic Complex of Pre-Aravalli age. The deposit extends
over a strike length of 16 kms in horseshoe shape with average thickness of 15 meters.
Detailed prospecting was carried out by the state department of Mines & Geology, which located
this deposit. A reserve of 77.0 million tonnes of rock phosphate has been proved on the basis of
60,000 mts. drilling in 500 bore holes. Out of these 17 million tonnes is of +30% P2O5 grade
and rest is of 12 to 30% P2O5
A beneficiation plant of 2000 tonnes per day capacity has been installed to up grade the low grade
phosphate having 16 - 17% P2O5 to 34% P2O5 Presently M/ s. Rajasthan State Mines & Minerals
Limited, a state government undertaking is doing mining in part of the area.
In addition to above small occurrences/ incidences of phosphorite were also located near Amberi(
10 km. from Udaipur on Udaipur Rajsamand road), Berwas (8 km. From Udaipur on Udaipur
Chittor road, Undari (16 km. from Udaipur on Udaipur ) Jharol Road.)
(ix) Apatite deposit:
The Apatite deposit is located near Niwania-Kikawas villages about 60 km. east of Udaipur.
Apatite occurs as thin veins and stringers, crisscrossing a large mass of crystalline limestone of
Aravalli Supergroup over an area of about 1.5 sq. km. Based on geological investigation by 912.52
mts. drilling in 28 bore holes, about 30,000 tonnes of apatite with 32-35% and one million tonnes
with 6 to 9% P20s were estimated in Kikawas area. 500 tonnes of apatite with 32-35% P 20S
content were estimated in Niwania area.
Banswara District
(i) Sallopat deposit:
Phosphate rock associated with the dolotmte chert horizon of Aravalli Supergroup was located
near Sallopat, about 67 kms. SW of Banswara. The phosphorite zone 120mts. to 280 mts wide
extends over a length of 1-2 km. in NW-SE direction. Within this zone several lenses of phosphate
rock of different sizes and grade are present. The grade of the mineral varies from less than 10%
P2O5 to 20% P2O5
Small occurrences of rock phosphate were also located near Ram-Ka-Munna and Jhermoti
Villages.
Siker District
(i) Kerpura deposit:
The apatite deposit is located near Kerpura Salwari villages in rocks of Delhi Supergroup
and Post Delhi intrusives. Apatite occurs as irregular veins, stringers and disseminations in
quartz veins, amphibolites and granite pegmatites intruded in garnetiferous biotite schist.
A reserve of 21,520 tonnes of ore containing 15.14% P20s has been proved with another
16,000 tonnes of 15% P 20S grade in probable category.
Jaipur District
Rock phosphate occurrenceswere located near Achrol village on Jaipur-Alwar road. Phosphorite is
associated with phyllite of Alwar formation. The P20s content is quite low and is about 5% only.
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Alwar District
The occurrence of phosphorite were reported from Rajgarh teh. of Alwar district. Near Aduka
Adwani hills G.S.I. has located small band of phosphorite associated with horn stone breccia of
Alwar formation. The analytical results reveal that the P 20S content is up to 11% only.
Year
Production(thousand tonnes)
1992-93
1993-94
1994-95
1995-96
617.42
1033.82
1096.65
1345.58
SPECIFICATIONS OF PHOSPHATE MINERALS FOR INDUSTRIAL
USES.
Phosphorus, Nitrogen and Potash are the three main plant nutrients. Phosphorous plays an
impOrtant role in root development and in the synthesis of protein, fats and carbohydrates.
Its deficiency in the soil can be made up by adding natural or manufactured phosphorous
bearing minerals/rocks. Apatite and rock phosphate are the two important minerals of
phosphorous. Apatite is of two types Le. chlorapatite hav ing composition 3Ca3 (P04)2
CaCl2, and fluorapatite having composition3Ca3 (P04)2 CaF2, Apatite is of igneous
origin and is found in veins. Rock phosphate is a secondary substance formed due to the
accumulation of organic remains like bones and by replacement of limestone, calcite etc.
by phosphoric solution to form a mixture of calcium phosphate. It does not have a definite
chemical composition. These minerals are mostly utilised for the manufacture of chemical
fertilizers like superphosphate, dicalcium phosphate, triple superphosphate, mono
ammonium phosphate, dlammomum phosphate and other complex fertilizers. Apatite and
rock phosphate are also utilized for the manufacture of phosphoric acid(H3P04) which in
turn is utilized for the production of pure chemicals like sodium phosphate, monocalcium
phosphate, dicalcium phosphate etc. The other important uses of apatite and rock
phosphate are in the manufacture of elemental phosphorous and in soil reclaimation by
direct application to soil in ground form. Important uses of Rock Phosphate are shown in
Figure 1.
Since the commercial exploitation of rock phosphate at Jhamer Kotra commenced a
lot of discussions about the specifications of rock phosphate required by phosphoric acid ,
single super phosphate and elemental phosphosphrous manufactures have taken place at
various forums. By and large, rock phosphate having the following specifications is
acceptable to the consuming industries
A. Rock Phosphate
1. Wet Process Phosphoric Acid
P2O5
32% (min)
SiO2
5% (max.)
CO2
4.5% (max)
LOI
5.0% (max.)
Fluorine
4.0 % (max)
Chlorine
150 ppm (max)
MgO
0.5% (max)
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2. Elemental Phosphorous
Phosphate rock of a lower grade can be used for the production of elemental phosphorous.
Rocks containing as low as 24% PzOs and as high as 23% SiOz with 3% iron and 7%
alumina can be used. The slag forming component like CaC°3' MgC03, F Z03 etc. should
be as low as possible.The rock should be hard and compact so that it can directly be
charged into the furnace. High content of slag forming impurities will require excessive
SiOz resulting in the dilution ofPz05 content in the charge.
The ISI (IS: 11224-1985) has prescribed the following specifcation of elemental
phosphorous (Type I) and phosphoric acid (Type-II)
3. Single Super Phosphate
The P 205 content in rock phosphate for the manufacture of single super phosphate should
have a minimum of 31 % P Z05' SiOz up to 8% can be tolerated, Iron and alumina Le.
Rz03 should not be more than 3.5%
Higher Rz03 may tend to reversion of available P Z05 (water soluble P Z05)' Carbonate
upto 5% will improve the reactivity of rock phosphate by increasing the reaction
temperature and also by making the mass porous.
4. Direct application of rock phosphate as fertilizer
The use of rock phosphate for direct application as fertilizer depends on its level of
solubility in the acidic soil. This application is dependent-upon the structure and chemical
composition of the rock. Mineralogical tests should be done to assess the sui tabili ty for
direct application. It is stated that carbonate radical is responsible for the reactivity of
directly applied P20s in the rock. According to ~PCL the following can be considered as
specifications for utilising rock phosphate as phosphatic fertilizer for direct application in
acidic soil.
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1. Absolute citrate solubility index
2. Apatite, carbonate ratio
CO2 % /P2O5 %
3. Origin of rock phosphate
4. Mesh size
5. Hydro oxyle ion in crystal lattice
is higher indicating substitution
of OH for P04 : H2O content
6. Grade of rock phosphate powder
7. Iron as Fe203
7% max.
0.035
Sedimentary
100
2%
16%
5%
8. CaO: P2O5 ratio
1.80
B. APATITE
The specifications of apatite for fertilizer industry are the same as that of rock phosphate
discussed above.
Apatite is also applied directly to the soil. According to the present practice in India
the average P20s content in the ore should be 16%. The iron content should normally be
less than 50/0 . However, the field tests are the more difinite criteria for the selection of
low grade apatite for direct application to the soil.
FUTURE TRENDS
In India most of the existing phosphatic fertilizer Plants and phosphoric acid plants were
designed on the basis of high grade imported rock phosphate. The Indian deposits are
generally of low grade. Therefore, the plants that may be set up in future will have to be
designed to accept indigenous rock or a blend of imported and indigenous ones. Trend
indicate that supplies from world markets ~re also showing decline in grade. In short the
user industries in future will have
to orient themselves to allow higher limitations of deleterious constituents.
Beneficiation of low grade ores is another forward looking step. Considerable
progress has been achieved in this field and significant success has been achieved at pilot
,plant stage. Already beneficiation plants have been set up by Rajasthan State Mines &
Mineral Ltd. at Jhamar Kotra and HZL at Matoon. It appears to be necessary to set up
additional plants in other areas.
PRESENT STATUS OF CLASSIFICATION OF RESERVE ACCORDING TO ITS
INDUSTRIAL APPLICATION
In the inventory of rock phosphate deposits as on 1.1.85 , only the key constituents namely
P 20S has been considered for gradewise classification of reserves.
Rock phosphate.
(a) + 30% P20S
Useable in manufacture of chemical fertilizer phosphoric
acid and elemental phos phorus.
(b) 25 to 30% P2O5
Blendable with + 300/0 P 20S high grade for manufacture of
chemical fertilizer.
(c) 20 to 25% P2O5
Useable for direct application to soil.
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(d) 11 to 20% P2O5
Beneficiable
(e) (-) 110/0 P2O5
Low, not useable at present.
(Conditional resource)
RECOMMENDATIONS FOR STANDARISATION OF GRADES
For this the different end-use application for purpose of reserve estimation keeping in view
the broad limitations of the exploration has been considered.
After examining the specifications of the user industries and the future trends of
beneficiation, the following end use classification of reserves for both apatite and rock
phosphate have been recommended by the comittee constitued by Govt. of India
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