MINERAL WEALTH OF BALOCHISTAN

Mahmood Siddiqui & Uzma Mahmood

 

HIDDEN TREASURES:

MINERALS ROCKS AND ORES

Natural substances are grouped into three major categories: Animal, Vegetable, and Mineral kingdoms. Members of the animal and vegetable kingdoms comprise living things that need air water and food to live and grow. In absence of these they will soon die and the bodies decompose. Aging process affects living things and with passage of time they become old and finally expire even in presence and availability of life sustaining environment. Contrary to this, minerals are nonliving substances and absence of air and water does not affect them. Change of environment, however, may cause some of the minerals to decay and disintegrate. Minerals are not affected by the ageing process and if left alone they will continue to exist in the same form and condition for indefinite period of time. Most of the minerals occur as crystals or in crystalline forms and in favourable circumstances may even grow in size as more material is deposited on the already existing crystal faces. Unlike living things, however, such growth is only at the external surface and does not take place from within. Minerals and rocks, being non-living materials, do not excrete, reproduce young ones, and lack all the biological systems that are character features of living souls.

 

Minerals

 

Term “mineral” to the common man is something that is extracted from the Earth's crust and invariably carries economic worth. If asked he may name a few minerals, like coal, sulphur, ironstone, etc. Economic geologists group minerals of commercial value in economic mineral category. Other minerals, which are normally of no use except constituting rocks, are called rock-forming minerals. Nature, however, does not recognize such a division. John Playfair, a strong supporter of Hutton’s plutonist-vulcanist theory for origin of mineral veins, expressed this in 1802 in following words:

 

Besides, what we are pleased to call the riches of mines, are riches relatively to a distinction which nature does not recognize. The spars and veinstones which are thrown out in the rubbish of our mines, may be as precious in the eyes of nature, as conducive to the great object of her economy, and are certainly as characteristic of mineral veins, as the ore of silver or gold, to which we attach so great a value.

 

In fact economic significance has nothing to do with the term mineral. A mineral may carry no economic worth yet it is a mineral. The term actually refers to the Earth's material without consideration to its monitory worth. In modern industrial age almost all naturally occurring substances—mineral or non-mineral—are used in industry and at home and thus carry little or significant economic value and nothing is absolutely worthless provided it occurs at a convenient place and is available in sufficient quantity to meet the domestic or industry requirements. The category of uneconomical or non-economic minerals, which was used in past to make distinction between worthless and valuable minerals, now refers to those minerals that do not occur in sufficient quantity or at convenient locations.

Minerals and rocks that exist today on the Earth, were formed on or within the Earth’ crust except of course “Hajr-e-Aswad” which, according to Islamic belief, came from heaven and the meteorites or shooting stars that occasionally reach the Earth from outer space.

Minerals are grouped into two major categories: metallic and nonmetallic. Metallic minerals are those from which one or more metals are extracted. The nonmetallic ones, in view of their principal use, are further divided in to industrial minerals, fuel minerals, gemstones, chemical minerals, fertilizers, etc. Over 2,000 mineral species are currently known. A few of these, like coal and diamond, occur only in free elemental state. Some others, like minerals of sodium, potassium, chlorine and fluorine are found only in compounds. A large number of minerals, however, transpire in free as well as in compound forms. Selective examples of some such minerals are given in the box below:

Minerals that Occur in Native or

Free State and in Compounds

Native or Free States

Gold, silver, copper, sulphur, carbon, graphite, diamond, etc.

Compounds

Sulphides (sulphur compounds  compounds):

galena (PbS), sphalerit (ZnS), chalcopyrite (CuFeS2).

Tellurides (Au, Ag, Te compounds0:

Sylvanite (Au, Ag) Te2, Calaverite (Au, Ag)Te2 , Petzite (Ag, Au)Te; and Nagyagite (sulpho-tellurited of Pb and Au).

Oxides (oxygen compounds): hematite (Fe2O3), corundum (Al2O3), cuprite (Cu2O).

Halides (chlorine & fluorine compounds): halite (NaCl), Fluorite (Ca2F).                        

Carbonates (carbon compounds): calcite (CaCO3), dolomite CaMg(CO3)

Sulphates (sulphur and oxygen compounds): gypsum (CaSO4). 2H2O,anhydrite (CaSO4).

Phosphate (phosphrous compounds): apatite [(Ca5 (PO4)3 (F)].

Silicate (silicon & oxygen compounds):

K-feldspar (KAl2Si3O8), olivine [Al (SiO5)(OH)4], pyroxene, micas.

Silicates (silicon & oxygen compounds): quartz (SiO2), K-feldspar (KAl2Si3O8),

olivine [Al (SiO5)(OH)4], pyroxenes, micas etc.

 

 

Rocks

Rocks are portions of the Earth’s crust that has no particular shape. It may be composed of single mineral or a group of minerals. Term “rock” gives impression of hardness and toughness and to conceive relative hardness of something it is often said that the thing is as hard as a rock. Geologically speaking, however, others are not so. For example clay and chalk are so soft that they can be easily scratched by fingernail. Other rocks, like granite and quartzite are so hard that it is not possible to scratch them even by a penknife. The appearance or look of rocks; the texture, is an important feature that is used to identify and classify rocks in groups. Rock texture depends on grain size of the constituting minerals and the way the grains are arranged. A rock may be coarse grained if constituents can be identified by naked eye, or fine grained if they are not so visible. Some rocks carry substantial commercial value and are used in different industries. Phosphorite, a phosphate bearing rock for example, is used as fertilizer, marble is used in construction industry and limestone and dolomite are used in manufacture of cement. These rocks, therefore, are included in economic minerals.

Ores

Metallic minerals occurring in native state generally need little or no refining, but those that occur in compounds, like sulphides, oxides, etc require thorough treatment to separate the metallic contents from the non-metallic ones. The metallic raw material that comes out of mine is called ore.  It is seldom composed entirely of useful minerals and always carries associated non-metallic minerals and rocks of no commercial value. These associated minerals and rocks are removed either before or during the refining process. “Ore” is thus a mixture of useful metallic components and the associated non-metallic waste material called “gangue”.
         

METALLIC RICHES OF BALOCHISTAN

            Balochistan is known to host good potentials for the metallic minerals, yet except chromite (chromium ore), none were being mined till recent past. Lately, however, mining of copper-silver-gold ore, in addition to that of chromite, has begun in Chagai district. Reasons for the past inactivity were many; main ones being non-availability of sufficient technical information on the ore deposits, insufficient knowledge and know-how of ore mining, and lack of investors willing to invest in high-risk mining venture. A short discourse on the metallic minerals of Balochistan is dealt hereunder. In spite of favourable environments and setting certain minerals have not be discovered in the province till present. In such cases, possibilities of new finds and favourable areas have been indicated.

Aluminium Minerals

Aluminium or aluminium (USA) (Al) is the lightest major metallic element with atomic number 13; atomic weight 26.27; specific gravity 2.70; electrical resistivity 2.669; and the melting point 660o C. It is the third most abundant element, after oxygen and silicon that makes up to 8.05 percent of the Earth’s crust. Main aluminium ores are:

Bauxite     (Al2O3. 2H2O)

Cryolite     (Na3 AlF6)

Alunite      {KAl3 (SO4)2 (OH)6}

Leucite     (KAlSi2 O6)

Kaolin       (H4Al2Si2O9)

Dawsonite {Na3 Al (CO3)2. 2 Al(OH)3}.

Uses: Light weight and toughness of aluminium coupled with excellent electrical conductivity permits extensive use of the metal in manufacture of aircraft body and power transmission cables. Bulk of metal is used to make alloy with copper, manganese, nickel, zinc, magnesium and silicon. It is also used considerably in building and construction industries. To reduce the fuel consumption, aluminium is also used in manufacture of lightweight automobile bodies. Other lightweight and durable items made of the metal include furniture, packaging materials, canes and foils, window frames, refrigerators, deep-freezers, and many other electrical appliances. Aluminium powder, which oxidizes instantly, is used in production of explosive called Alcoa Alunit.    

Formation of Ores:  Bauxite, the principal aluminium ore, forms as a result of typical surface weathering process known as Laterization. The process occurs in warm and moist tropical regions, particularly in gently sloping, poorly drained limestone terrain. Sub-aerially weathered constituents of the rocks, e.g., lime, soda, magnesia, silica, etc., are removed in solution and limonite (iron oxide) together with alumina, diaspore, gibsite, boehmite, etc, are left in situ as a mineral aggregate known as Laterite. When concentration of alumina in the laterite is high and that of the limonite correspondingly low, the aggregate is termed Bauxite, and is excellent aluminium ore.

Occurrences in Balochistan:        Laterite occurrences have been reported from Ziarat area of Balochistan. Zones of high aluminium concentration are suspected in these laterites which needs detailed geochemical investigations. In Jamaica high grade bauxite deposits are hosted in White Limestone Formation of Middle Eocene-Lower Miocene age. Many sinkholes have developed in this karst topographic country that hosts thickest bauxite occurs. Here the ore contains 48 to 50 percent alumina with 18 to 20 percent iron oxide and the reserves are estimated at several hundred million metric tons. Fairly good chances of presence of bauxite in similar limestone terrain in Lasbela-Khuzdar-Kalat-Quetta-Zhob mountain belt are predictable. Large sinkholes and caves developed in limestone exist, particularly in Bolan district of Balochistan. These and other sinkhole areas occurring at many places may be specifically explored for bauxite.

Price: Price of aluminium in London Metal Exchange in early May 2008 was US $ 1.3 / lb.

Antimony Minerals

            Antimony (Sb), with atomic number 51; atomic weight 121.75; isotopes 121 and 123; melting point 630o C and specific gravity 6.62, is a metallic element of “minor metals group”. It rarely occurs in free metallic state in nature and averages in the crust to about 0.3 ppm (parts per million). 

Principal antimony ore is Stibnite or Antimonite, (Sb2S3). Other oxide and sulphide ore minerals are:

Senarmonite             (Sb2O3)

Valentinite                (Sb2O3)

Cervantite                (Sb2S3.Sb2O5)

Kermesite                (2Sb2.S3.Sb2O3).

Antimony also occurs in association with silver, lead, and copper as sulphides called sulphantimonites. Important ores are:

Staphanite               (Ag5SbS4)

Pyrargyrite               (Ag3SbS3)

Jamesonite               (Pb4FeSb8S14)

Bournonite                (CuPbSbS3),

Tetrahedrite              {(Cu,Fe)12Sb4S13}

            Uses: Antimony, being a minor metal, is used relatively in small quantities. Principal use of the metal is in production of various lead alloys to which it imparts stiffness and hardness. Such alloys are used in storage battery plates, in the manufacture of anti-friction bearings, type metal, solder, cable sheath, pipes, bullets, tracers, detonating caps, decorative castings and in a number of other engineering products. The metal is also used in manufacture of antimony trioxide (Sb2O3), which is used in manufacture of flame-retardant chemicals and in smoke screens. Various compounds of the metal are used for enamel, white, black, yellow, vermilion and orange pigments, as rubber vulcanising agent, in production of chemical and photographic materials and to protect fabric from flames and sunlight. Minor use of the metal includes its use in the striking face of safety match box and as surma for darkening the eyelids.

Formation of Ores: Antimony ore (stibnite) generally occurs in small, shallow, discontinuous deposits formed by the terminal phase of hydrothermal fluids. These fluids travel a long way from the magmatic source and by the time the ore is deposited they would have lost most of the heat and energy to chemically react with the surrounding rocks. Consequently, host rocks, except limited silicification, pyritization, and carbonatization, most often remain unaltered. Cryptocrystalline (very fine) silica may replace limestone near the ores and scattered pyrite may define a zone of reduced iron in clastic sediments. No conspicuous alteration halo is formed around the ore-body but argillisation of porous sediments often bleaches wide area near telethermal deposits. The ore is generally deposited in aphanitic to very coarse-grained crystal forms by replacement and precipitation in open-space (fissures, joints, and rock pores). Crystal-lined vugs, comb structures and rhythmically banded ores are common forms of occurrence. In carbonate rocks replacement is the dominant form of ore deposition. Circulation of fluid and deposition of ores are controlled by fault system. A few examples of telethermal deposits include Kennecott copper deposit, Alaska; Mansfeld copper-lead-zinc deposit, Germany; Mississippi Valley Tri-State lead-zinc and fluorite deposits, and Colorado Plateau and Wyoming uranium-vanadium deposits, USA.

            Occurrences in Balochistan: Antimony ore, mainly stibnite occurs near Qila Viala and Haji Sardar areas in Qila Abdullah district. Unconfirmed mineral occurrences are also reported from Kharan district.  In both the districts, which are hundreds of km apart, the ore occurs in same tectono-metallogenic (or tectono-stratigraphic) zone—the Balochistan Flysch Basin.  In Qila Abdullah district, the ore is associated with quartz veins in quartzitic sandstone and shale of Shaigalu sandstone in Khojak Formation of Oligocene age. Hosted within the Chaman transform fault system, these occurrences, according to Sillitoe (1978), were possibly generated during faulting and the related deformation stages. Detail exploration on none of these occurrences has been carried out so far and it is not known as to what depth and lateral extent the mineralization extends. The light- to dark-brown oxidation zones, with which the mineralization is associated at the surface, is 15 to 70 metres wide and extends up to about 700 metres in length. The zone of mineralization, elongated along the associated fault zone, spread in about 5 km area. On the basis of wide oxidation zones, Ahmad (1975) concluded, “the favourable area is considerably large and the reserves, when estimated after thorough exploration, would increase”. Qila Abdullah prospect was worked in the past at a small scale, but due to very limited demand of the minerals in local market, the mining was discontinued. Analysis of seemingly high grade of ore from the area, according to Ahmad (1975), indicated about 54.29 percent antimony. Other elements present are barium 10.73 %, iron 3.36 %, lead 0.3 %, arsenic 0.22 % and mercury and zinc in traces,

Up-gradation of ore: At Krinj mines in Chitral, more or less similar ore as that in Qila Abdullah, was being converted to antimony trioxide (Sb2O3) in a simple, diesel-operated, plant at the mine head and the product was trucked to Karachi for export.  The Qila Abdullah and Kharan district antimony ores also, if found feasible after detailed and systematic study, can be treated the same way. Antimony ores are often known to contain substantial concentration of gold and silver, which considerably upgrades the ore price. It is however, not known if the Qila Abdullah and Kharan district antimony ores do contain gold / silver contents. If they do, the two noble metals can be extracted out of the ore and sold as preferred and favourite by-products separately, before the remaining ore is converted to antimony-trioxide.

            Price: Antimony metal (99.65 %) of Huachang China in early May, 2008 was selling @ Us $ 6638 / MT and price of Antimony trioxide (99.80 %) during the same period was US $ 5730 / MT (Metric Tons).

Chromium Minerals

            Chromium (Cr), atomic number 24; atomic weight 52; isotopes 50, 52, 53 and 54; melting point 1903o C; and specific gravity 7.2, is a metallic element of ferroalloy group. It does not occur in nature in free-state. The average amount of chromium in ultramafic rocks is 2000 ppm; in mafic rocks 300 ppm; and felsic rocks <25 ppm. Chromite (FeCr2O4) or (FeO.Cr2O3), with theoretically 68 percent Cr2O3, is the only ore that yields chromium metal.

            Uses: In the United States, which is the biggest consumer of chromium, 62 percent of the metal is used in metallurgy, mainly in producing alloys; 20 percent in chemical industries; and 18 percent for the refractory purposes. Chromium makes alloy with iron, nickel, and cobalt. The alloys are strong, tough, hard and resistant to oxidation, corrosion, abrasion, chemical attack, and high temperature breakdown. Special chromium alloy stellite employs tungsten, molybdenum and cobalt, in addition to iron, yields hard steel for high-speed tools. Specification of metallurgical grade chromite is minimum of 48 percent Cr2O3 with Cr:Fe ratio of 3:1 and maximum 8 percent SiO2.. That required for production of corrosion resistant stainless steel, is 13 percent chromium. Some chromium is used to produce steel and cast iron and for chromium plating. Chemical grade chromite is required to contain a minimum of 44 percent chromium and maximum 5 percent SiO2. The commodity is used in production of pigments and paints, in tanning leather and textile dyes, for corrosion resistant coating, as a catalyst and in the drilling mud chemicals. Refractory grade chromite is to contain a minimum of 31 percent Cr2O3 with a maximum of 12 percent Fe and 6 percent SiO2. The commodity is used in production of refractory bricks that are used in lining open-hearth steel furnace.

            Formation of Ores: Lower part of the oceanic plate is mainly composed of ultramafic rocks; dunite and peridotite. These rocks quite often contain disseminated chromite grains. The dissemination sometimes gets rich enough to produce reasonably rich chromite zones. During subduction of the oceanic plate under continental crust, often-sizeable pieces of the oceanic crust along with rich chromite zones are held at the subduction sites. These allochthonous (transported) blocks produce podiform or Alpine type chromite deposits. In Balochistan, chromite occurs in such podiform deposits, which are small and contain a few thousand to a few hundred thousand tons of the ore. Podiform chromite deposits are generally small as compared to the magmatic segregation deposits, like that as produced at the Bushveld igneous complex in South Africa, which promises about two billion tons of the ore.

            Occurrences in Balochistan: In association with ultramafic rocks, chromite occurs in the Ophiolite Thrust Belt near Muslimbagh in Zhob district, Qila Saifullah district, Khuzdar and Lasbela district, and in the Ras Koh Range in Chagai and Kharan districts. The Zhob district chromite deposits were producing 20,000 to 30,000 tonnes of ore annually and the Jang Tor Ghar group produces best grade of the ore. Total ore reserves, contained in hundreds of the occurrences in the area scattered in a 55 mile long and from a few to 20 miles wide belt, have not been estimated precisely. According to Ahmad (1975), nearly a million tons of ore was mined out from the deposits by the year 1975.  Presently, most of the production (35,000 to 40,000 tonnes) of the ore comes from Qila Saifullah area. Muslimbagh  chromite, containing about 48 % Cr2O3, is classed as good quality ore.

In Chagai and Kharan districts and in Kalat area, Chromite occurs in small isolated lenticular bodies in ultramafic rocks associated with ophiolitic blocks near locality known as Nag, in Rayo Nai valley and at Gau Koh ridge, Ras Koh Range. Reserves of the ore have been estimated at 10,000 tons at Rayo Nai valley and about 10,500 tons in Nag and Bunap areas. Intermittent mining of the mineral in Chagai, Kharan and Khuzdar districts is in operation.

            Price: Chromium concentrate 43 %, in China in early May 2008 was selling @ US $ 355/ MT.

 

REFERENCES

Ahmad, Z., 1975, Geology of Mineral Deposits of Baluchistan: Rec, v. 36, Geol. Surv. Pak. 178 p.

Sillitoe, R. H.., 1978, Metallogenic evolution of a collisional mountain belt in Pakistan (a preliminary analysis): Jour. Geol. Soc, v. 135, pt. 4. pp 377-387.