Ore mineralization at Rampura-Agucha is represented by sphalerite, pyrrhophyllite, pyrite, and galena with minor amounts of chalcopyrite, arsenopyrite, talhore and boulangerite. The ore minerals are hosted essentially in the Precambrian graphite-sillimanite-bearing quartzo-feldsphathic gneiss and schist, and calc-silicate rocks. Petrography of drill-core samples shows that the ore minerals have been metamorphosed together with the host rocks under upper amphibolite facies conditions at pressure and temperature in the order of 6.2 ± 0.4 kb and 680° ± 30° C, respectively. Quartz and tourmaline from pegmatite contain independent CO₂ (+CH₄) and aqueous fluid inclusions. Intersection of CO₂ and H₂O isochores shows that the tourmaline and quartz in pegmatite formed at much later stage (300° C and 0.64 kb). Substantial part of footwall side of the orebody was involved in dynamic metamorphism subsequent to regional metamorphism.

The Precambrian formations of Western India host a unique lead-zinc deposit near Rampura-Agucha. The deposit contains an estimated sixty million tonnes of ore having an average grade of 13.48% Zn and 1.935 Pb. The ore is hosted in highly metamorphosed Precambrian formations having characteristic silicate and sulphide assemblages and textures. On the basis of field evidence, petrography, petrochemistry and nature of mineralization, it is concluded that the Rampura-Agucha lead-zinc deposit represents a synsedimentary-metamorphosed type of deposit. Tectonic activity and major orogenic cycles (Aravalli c. 1800 and Delhi c. 1250) brought about characteristic changes in the synsedimentary orebody into a high-grade metamorphosed (mobilized and remobilized ) massive sulphide deposit. Recrystallization and redistribution of chemical components were promoted by regional metamorphism under high P-T conditions. Dynamic metamorphism followed regional metamorphism, which produced coherent finely granulated ore containing rounded fragments of host rock and those of pyrite (ball texture). The orebody underwent prolonged weathering producing a thick cap of gossan, significantly enriched in zinc.       

World's largest anthophyllite and tremolite deposits occur as small pods and lenses in the Precambrian ultramafic rocks of South Rajasthan. These deposits are being exploited by small-scale manual, opencast mining methods. The recovered ore is pulverized, without beneficiation, for use in asbestos-cement products that are manufactured in the small-scale industrial units throughout the country. Field survey conducted for mining, milling and processing units did not yield anomalous health hazards results. The industry falls under the "extremely low-risk" category of the "Notion of acceptable risks". The paper attempts to rationally examine the facts and fallacies associated with asbestos mining and focuses attention on its risk-benefit aspect. It is concluded that the curbs imposed on asbestos are not justified.

Keywords: Asbestos, Mineral Economics, Health Hazards, Rajasthan

Right or Wrong?
The author of ' Death inside the factory gates" (Down To Earth, Vol 9, No 9; September 30) has not done justice to the article. Ecoweapons have been successfully used the world over. The ban on asbestos products in USA is a result of successful use of "ecoweapons" adopted by the synthetic fibre lobby of USA. The asbestos products manufactured in USA were mostly being imported from Canada. In 1991, the federal appeals courts of USA reversed the ban imposed by the Environment Protection Agency. The court, after a prolonged legal battle, found that evidences against asbestos products were unsubstantiated or misinterpreted.

It felt that the replacement of asbestos does not reduce the projected dangers, rather increases indirect risks. For example it stated, " Credible evidence suggests that non-asbestos brakes could increase significantly the number of highway fatalities." Based on the notion of acceptable risk, statistical evaluation of the lifetime risk value indicates that asbestos falls under ' extremely low risk category.' The lifetime risk value is just 10 per million for asbestos. For tobacco, the figure is 219,000 per million, automobile accident is 16,000 per million, alcohol drinking, air travel and for skiing it is 7,300 and 2,000 per million respectively. Therefore, I hope that your magazine resists temptations to utilize 'ecoweapons.' Readers expect unprejudiced assessment to a problem. The author should have discussed the myths as well as realities, rather than highlighting the myths and ignoring the realities.

P.S. RANAWAT
Udaipur, Rajasthan.

PREFACE
Mining is the oldest industrial activity of human beings. It started with the first stone that man hurried to get his food. Today, agriculture and mining are the two basic human activities necessary for human survival and progress. For the state of Rajasthan, Madhya Pradesh, Bihar, West Bengal, Orissa, Karnataka, Assam and couple of other states of the Union, both of these activities play important role in their socioeconomic development. Most of the mineral resources of India fall under the small-scale category so do the industries based on them. Environmental impacts due to utilization of this category of resources need to be appraised and a proper strategy has to be evolved for sustainable development. 

MINERAL RESOURCE UTILIZATION - WITH ENVIRONMENTAL AWARENESS

(Copy of the letter dt.Oct.06, 1993 to the P.M. on personal letterhead).
06-10-1993

SHRI NARSHIMA RAO 
Prime Minister of India
PMO, South Block.
NEW DELHI.Hon'ble Sir,

This is in reference to policy confusion going on in the country during past couple of years regarding the impact on environment owing to exploitation of our mineral resources. In this connection it is pertinent to note the following:

Fluorite and associated minerals were collected from Mando-ki-Pal (Dungarpur Distt.), Chowkri-Chhapoli (Sikar-Jhunjhunu Distt.), Asind (Bhilwara Distt.) and Jhalara (Udaipur Distt.) and studied for their fluorescence with the help of Blackwood type ultraviolet ray lamp emitting light with wavelength in 3650° A region. It was found that all the fluorites of Jhalara and Asind were non-fluorescent, while those of Mando-ki-Pal and Chowkri-Chhapoli area showed interesting results. From these two areas, green and yellow fluorite was in all cases found to fluoresce strongly, while the violet, brown and grey colored varieties were always non-fluorescent. Fluorite of mauve, purple, blue or white color was weak to fairly fluorescent. Relation of color of fluorite and its fluorescence is discussed. Minerals associated with fluorite were also studied. They include calcite, apatite, quartz, siderite, epidote, galena, sphalerite, ilmenite, copper, sulphides, pyrite, copper-carbonates and cerussite. Of these minerals only a few calcites of Mando-ki-Pal showed red, and in one case pinkish white, fluorescence. Cerussite associated minerals were found to be inactive. Activators responsible for fluorescence in these minerals are discussed.Varied intensities and different colors of fluorescence have brought out several textural features, which are otherwise not evident in hand specimen. Utility of fluorescence in study and interpretation of textures is emphasized.

Phosphorescence was, however, not seen in any of these minerals.

Fluorite mineralization has been encountered in Post-Delhi tonalites exposed near Salwari, 15 kms. ENE of Khandela (27° 36': 75° 33') in Sikar district of northern Rajasthan. The rock has intruded Ajabgarh garnetiferous biotite schist and its feldspars have been highly kaolinized due to the action of mineralizing solutions.  Fluorite is either massive or occurs as octahedral crystals in fissures and weak planes. Replacement of calcite and/or the host rock is also observed. Zoning of green, purple and blue fluorite is generally noted which indicates its rhythmic precipitation from the mineralizing solutions. In a single crystal, measuring 5'' of c-axis, thirty-six bands of fluorite have been counted. Apatite mineralization is seen in the area completely surrounding the fluorite occurrence, i.e.. while fluorite  is concentrated at the center of intrusive body, apatite occurs all around it in tonalite, biotite schist, hornblendite, vein quartz and hybrid rocks. Thus a lateral zoning of apatite around the fluorite deposit has been recognized.Besides fluorite and apatite other minerals formed in the area include calcite, quartz, ilmenite, magnetite and some sulphides of copper and iron.The fluorite-apatite mineralization is attributed to the hydrothermal solutions genetically related to the Post-Delhi acid igneous rocks of the area.

The following two papers were presented at the II Session of the Indian Geological Congress, 1978 (Udaipur)

Fluorspar mineralisation in Rajasthan occurs at five localities, viz. Mando-ki-Pal (Dungarpur Distt., South Rajasthan), Jhalara (Udaipur Distt., South Rajasthan), Asind (Bhilwara Distt., Central Rajasthan) Chowkri-Chapoli (Sikar-Jhunjhunu Distts., North Rajasthan), and Karara (Jhalore Distt., South West Rajasthan). Of these, the first four are located along a nearly NNE-SSW axis running across the state. Based on fluid inclusion studies, it is concluded that these deposits formed independently under varied physico-chemical environment of mineralisation, and that they are not located along a major lineament having common source, as one would be inclined to believe because of their single linear trend (cf. Van Alstine, 1976) At Mando-ki-Pal two phases fluid inclusions with high degree of fill are found in fluorites and associated minerals occurring in cataclastic and granitic gneiss host rocks. The stratabound fluorspar veins in quartzite (Nawagaon) have inclusions of liquid CO2 occasionally with halite daughter mineral liquid CO2 has not been found in fluid inclusions in fluorite from Jhalara area. They are biphase inclusions with small vapour bubble. At Asind, the fluorite contains multiphase fluid inclusions with more than one daughter minerals. Dissolved CO2 in aqueous phase is suspected at Jhalara. At Chowkri-Chhapoli, negative faceted cavities contain fluid inclusions of lower degree of fill and halite daughter mineral. The associated first generation quartz has inclusions with halite daughter minerals while the inclusions in younger quartz contain fibrous anisotropic daughter mineral.

Thus, a varied chemistry of mineralizing solutions depositing fluorspar in these areas is indicative of different sources and or different phases of fluorite mineralization.

The paper deals with fluid inclusion study of apatite, cogenetic with talc at undithal, Udaipur district. The data indicate that steatitization of ultramafic rocks was brought about by solutions of low salinity (3.80±1.64% NaCl), also low Xco2, having temperature in the region of 300°C -400 °C and pressure between 2-3 kb. PTX conditions have been deduced from the fluid inclusion study and mineral assemblage.

Two phases of fluid inclusions having a high degree of fill are present in fluorite, barite, and quartz of Karara area. In fluorite-I (Cubo-octahedral crystals or green coarse granular) bubble is present in fluid inclusions upon freezing, whereas in fluorite-II (columnar or cubic crystals on fluorite-I) the bubble is generally eliminated. Barite contains two-phase fluid inclusions with a very small vapour bubble or monophase inclusions, in letter vapour bubble nucleates on cooling the plate (not resulting in freezing) indicating that monophase fluid inclusions contain stretched liquid. Fluid inclusions in quartz-I, corresponding to fluorite-I stage of mineralization, also freeze with bubble retained.Fluid inclusions in which the vapour bubble is eliminated on freezing may show any of the following features (a) Vapour bubble reappears between -7°C and -3°C; (b) Vapour bubble does not reappear by 0°C and ice is present metastably up to +3°C; (c) Strain effect and development of cracks along cavity corners, in rare cases the ice breaks open the cavity. Freezing data for fluid inclusions showing features (b) and (c) have not been included in the freezing data for salinity determination.

Freezing temperature for all the minerals show that mineralizing solutions in both the stages of mineralization were of low salinity, 2.25 ±1.995 NaCl.

The paper describes the fluid inclusion study of fuchsite-quartzite occurring in Banded gnessic complex of Jagat area. Minerals other than fuchsite present in quartzite are ilmenite, leucoxene and rutile.

Primary fluid inclusions are present in quartz grains of the quartzite, which show aqueous phase and a vapour bubble. Trails of secondary fluid inclusions (biphase) are present. Primary and secondary fluid inclusions are small in size (2-18μ m). Upon heating the primary fluid inclusions homogenize in liquid phase, TH L-V =244 °C - 277 °C. Low density Co₂ has been observed in some of the primary fluid inclusions (dco₂ = 0.164 to 0.221).  Te range of -33 °C through -35 c indicates presence of MgCl2 in the aqueous phase, Tm of which gives salinity range of 8.94 to 18.79 eq. wt. % NaCl.

Pockets, lenses and veins of calcite occur in calc-silicate rocks of Delhi Supergroup of rocks (Proterozoic) near Saira, Udaipur district. Two phase primary fluid inclusions of rhombic shape are observed in calcite samples of one of the pits. Fluid inclusions homogenize in liquid phase by 110 °C. Freezing temperature (-3 °C to -1 °C) show that the solutions depositing calcite were of very low salinity. Characteristic feature of freezing is that vapour bubble reduces in size during melting of ice (-31 °C onwards), in some cases the vapour bubble is completely eliminated during thawing which reappears suddenly between -2.7 °C and +2.2 °C

Fluorspar mineralization occurs in pyroclastic and to lesser extent in flow rocks of volcanic vent near Karara, Rajasthan, northwestern India. The volcanic rocks of western Rajasthan belong to Malani suite, 505-735 m.y., and represents the largest silicic volcanic activity in India. The pyroclastic rocks near Karara are volcanic breccia, lappili tuff, and welded tuff including ignimbrite. Flows of mafic to silicic rocks are present. Three distinct stages of fluorspar mineralization are present as cavity filling. Two-phase primary fluid inclusions having high degree of fill are present. Th: Stage-I: 110°-240°C, Th: Stage-II: 50°-130°C. Mineralizing fluids had low salinity, 225 ± 1.99 equiv. Wt % NaCl. Phenocrysts in the saturated volcanic rocks contain melt inclusions (glass vapour bubble0, Th: 1050 ± 50° C

Narrow veins of fluorspar occur as fissure or joint filling in Precambrian migmatites near Asind (Bhilwara District). The area is essentially a migmatite terrain with intrusives of amphibolite, pegmatite and aplite. Veins and bands of epidosite and unakite are commonly observed. Fluorite is violet, purple or colourless granular and is rarely associated with quartz. Epidotization of vein walls is characteristic feature observed in the area. Fluorite contains multiphase primary and pseudosecondary fluid inclusions having an aqueous phase + vapour bubble + NaCl ± granular and/ or acicular birefringent phase ±± black opaque phase. The aqueous phase has RI nearly equal to that of fluorite, but the outline of the inclusion cavity (mostly irregular) become clear during heating and freezing runs. Type-II inclusions have a distinct relief and have only halite daughter mineral. Type-III inclusions also have distinct relief but are biphase. Quartz also contains multiphase or three-phase inclusions. The fluid inclusions freeze with difficulty to dark brown phase, freezing commences and ends in dendritic fashion. Cryometric data is Te: -57 ± 2° C, Tm hydrohalite: -50±5° C, Tm ice: -24 ±2.5° C. During the heating runs liquid-vapour homogenization usually takes place before dissolution of daughter minerals. Th L-V: 132°- 187° C, Th NaCl: 120° - 164° C, Th birefringent phase: 205°-262° C, the inclusions decrepetation leave brown residue on the surface of the plate.

The fluid inclusion and field studies show that the fluorspar mineralization in the area was brought about by concentrated solutions having high CaCl₂ / NaCl ratio (presence of Fe salts is also indicated) having minimum temperature of about 400° C and minimum pressure of about 1.5 kb. The fluorspar mineralization is possibly an outcome of late stage activity related to migmatization of the rocks of the area.

Precambrian as well as the younger rock formations in Rajasthan host a variety of geologically and economically important industrial minerals and rocks (nonmetallic or NM resources), which hold premier position in India’s economy. NM resources of the province can be classified into six genetic models, which are tabulated below. Sedimentary (Sed), metamorphic (Met), igneous (Ign), hydrothermal (Hyth), metasomatic (Mts), residual concentration (Rcn) and evaporation (Evp) processes played dominant role in this complex nonmetallic province. Except for the deposits formed by Sed and Rcn processes, most of other deposits display polygenetic imprints. The paper discusses genetic models and tectonic significance in formation of these resources. Minor quantities of barite, calcite, clays, dolomite, emerald, epidote, fluorspar, garnet (gem), graphite, jasper, kyanite, lignite, mica, oil & natural gas, ocher, potash, quartz, silica sand, vermiculite are also mined in the province.
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NM Resources: Genetic model; Formation; % of India’s production
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Amphibole asbestos: Met; Proterozoic; 90 %
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Clays: Rcn; Sed; Archean to Tertiary host rocks; 71%
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Feldspars: Ig; Precambrian; 70%
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Granite: Ig; Met; Precambrian & younger; Significant
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Gypsum, salts: Evp; Tertiary; 93%
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Limestone: Sed; Archean to Eocene; Significant, steel, cement,
chemical & decorative grades.
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Marble: Met; Proterozoic; 90%
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Rock Phosphate: Sed; Stromatolitic; Proterozoic; 75%
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Sandstone, Slate: Sed; Archean to Tertiary; Significant, > 70 %
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Serpentinite: Mts; Proterozoic; 100%
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Talc & Pyrophyllite: Met; Proterozoic; 87%
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Wollastonite: Mts; Proterozoic; 100%
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The state of Rajasthan is blessed with a rich variety of metallic as well as industrial (non-metallic) minerals (including rocks). Many of these are geologically unique deposits formed by varied genetic processes. Most of its Precambrian deposits have explicit metamorphic imprints on them.  Sedimentation and secondary processes are dominant in younger deposits. These mineral resources play an important role in economic sustenance of the people of the state and the country. Many of these deposits occur in wastelands and therefore the phobia of adverse effect of mining on environment is highly exaggerated.

The Western Indian State of Rajasthan has been the source of big, quality emeralds for centuries. Rich hauls of gems were recovered from placer and mother lodes in the schists associated with the belt of ultramafic rocks in the Precambrian formations. Modern mining started in 1943, and now the mining activity is at standstill. Jaipur, Rajasthan, is one of the most important trading and gem cutting centers of the World. Jewelers periodically approach us to identify stones; lately the need to distinguish between the Indian (re-cut) and South American gems has been felt. Two non-destructive techniques proved diagnostic. Studied South American samples showed halite bearing aqueous fluid inclusions and they display strong red fluorescence, where as the Rajasthan (Indian) emeralds contain carbonic fluid inclusions and do not show red fluorescence. With the help of these two non-ruinous techniques it is possible to identify the source of the gems. Similar characterization of emeralds from various locations of the World would be of great importance. Additionally, record of photomicrographs of fluid inclusions in a gem can serve as its identification mark (fingerprint) in event of its loss or theft. Emerald mineralization, in Rajasthan, occurs in biotite-/ talc-chlorite -/ actinolite ± horneblende schists that are associated with altered ultramafic rock intruding the Precambrian metasediments; close association of pegmatites is the second locus for its prospecting

Low-grade rock phosphate ore (9-10% P₂O₅), both primary and weathered varieties, were beneficiated using direct acid-circuit reverse flotation at pH 5.0. H₃PO₄ was used as a depressant of phosphate and sodium oleate containing a sulphonic acid was used to float carbonates. pH was adjusted by dilute H₂SO₄ to 5.0 prior to flotation. The phosphate concentrate (tails) of weathered ore analyzed 32% P₂O₅, 3.8% MgO and 62.4% recovery. Primary ore concentrate, after one scavenger cleaning yielded 34.4% P2O5, 2.5% MgO and 62.30% recovery.  

A simple method for the determination of work index, Wi, in wet grinding using lab size ball mill has been suggested. The method involves grinding at different times giving material, which can subsequently be used for m.o.g., Wi determination and flotation studies at a time. The Bond's Third Theory of Comminution is applied to determine grindability test (to a first approximation only).

It is said that British education system in India was aimed at producing “Babus” to sustain the British Raj. True or not, but the geology education in India produced sturdy field geologists or “babu” geologists (technical coolies) for the British Raj to take care of mineral resource exploitation in India. The curriculum of Geology Departments failed to produce good entrepreneurs to utilize mineral resources. Private enterprises did thrive under British Raj but they were mostly non-geologists. This anomaly was agonizingly felt when non-technical citizens became millionaires by utilization of mineral resources through mining or mineral based industries. Geologists were happy to be employed by these entrepreneurs – i.e. the educational system produced “Job-Seekers” rather than “Job-Creators”. This lacuna was not set right even after India attained independence.   The students of batches of late 60s and early 70s in Rajasthan raised this issue and wanted curriculum modified to take care of “Job-Creator & Resource Utilizer” aspects; but it was ignored because it was too bold a concept then, especially because of socialistic priorities of that period. The matter was partly resolved through organization of invited lectures. An article on “How to Become Mine Owner” was published in our Silver Jubilee Souvenir (1975), which served as a guiding light for number of our students. A couple of them gave up confirmed jobs in state government departments and Hindustan Zinc Ltd. to set up their own enterprises.   Subsequently, in the year 1982 the Government of India tried to promote entrepreneurship through the schemes of National Science and Technology Entrepreneurship Development Board (NSTEDB), which was established in the Department of Science and Technology, New Delhi. The education policy of 1986 emphasized the need for vocationalization of technical education at various levels “so as to focus attention on entrepreneurship and self employment in addition to their present mandate of churning out trained manpower”.  

It was felt that an attempt should be made to promote entrepreneurship for geology students.  Because it could not be done through change in curriculum, another mechanism was thought of. Consequently, an Entrepreneurship Development Cell (EDC) was established in the Department of Geology, Udaipur, Rajasthan, where in various training programs were arranged to create entrepreneurial culture in its students. It is suggested that a drastic change in curricula of Geology Departments is called for to produce “Job- Creators” rather than “Job-Seekers”.

psranawat@geolmlsu.orgBeneficiation of low-grade rock phosphate ore is being done at Jhamarkotra project Rajasthan since 1992; presently, 1500 tonnes per day (TPD) of ore is being upgraded to +34% P₂O₅. Studies are being carried out to improve both grade and recovery of P₂O₅ and to reduce the cost of beneficiation of this strategic commodity. This communication is to report our findings on bench-batch-scale beneficiation, both on reverse flotation and direct flotation, of Jhamarkotra dolomitic rock phosphate ores. Reagents used were 1-heptane sulphonic acid (synthesized in lab), N-lauroyl sarcosine and di-(2-ethyl hexyl) phosphoric acid. The use of individual reagents gave E.R. value ranging from 1.2 to 1.5. A mixture of reagents sodium oleate & sulphonate gave better results. A mixture of poor grade ore with calcitic apatite also gave better results (i.e. E. R. >2).

psranawat@geolmlsu.org

Surface modification of solid particles is a pre-requisite of flotation-beneficiation. This is achieved by adding suitable reagents, which are preferentially adsorbed on the surface; and formation of a least soluble compound on the solid surface is a condition of preferential adsorption. Following this reasoning, flotation-beneficiation of phosphate from Jhamarkotra dolomitic rock phosphate ores was attempted using added barium ions at pH 5.0 in reverse flotation and from 7.0 to 12.0 using direct flotation. Barium ions form the least soluble salt as compared to calcium and magnesium. The paper reports the results of our study.