Barite – more than a weighting agent

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Published: Monday, 03 June 2013

A person suffering from a gastrointestinal disorder is likely to undergo an X-ray test. Any possible ailment can be clearly examined in the presence of heavy metal and an inert substance with the ability to absorb X-ray radiation to highlight any abnormalities. The name of this heavy material is barium sulphate (BaSO4), or barite.

By Ajay Kulshreshtha, AK Minerals Consultancy Services

A person suffering from a gastrointestinal disorder is likely to undergo an X-ray test. Any possible ailment can be clearly examined in the presence of heavy metal and an inert substance with the ability to absorb X-ray radiation to highlight any abnormalities. The name of this heavy material is barium sulphate (BaSO4), or barite.

The use of barite in drilling is widespread, but its ability to act as a shielding material, as seen in the above X-ray example, is just one alternative use for a mineral with exceptional properties. It can be employed in numerous other applications, each of which provides an excellent business opportunity.

What is barite?

Barytine, barytite, schwerspath, barytes, heavy-spar, tiff, desert rose and blanc fixe are some of the other names for barite. The name barite derives from the Greek word βαρύς (heavy) and it indicates the element’s high atomic weight (molecular weight = 233.39 gm; see Figure 1). Barite, or baryte as it is sometimes spelled, is used for the naturally occurring barium sulphate only.

Barite’s large weight is attributed to the presence of the barium element in the compound. Barium belongs to the alkaline earth group, which seldom occurs in native form. However, it does occur in a very small quantity in igneous rocks. Barite is mostly found as barium sulphate compound in several parts of the world and is popularly termed as barite or baryte in trade.

It is largely seen as a weighting agent used in global oil and gas industries. This is because of its extremely high specific gravity, which prevents blowouts of oil, the collapse of the drilling-well wall and its ability to carry drill cuttings from the well bottom to the surface. Demand for barite from the oil and gas sector is rising, not only due to an increase in consumption, but also because of more demanding requirements as technological advancements see a deeper penetration of existing oil wells.

This sector alone uses up about 84% of global barite production. India - the world’s second-largest barite producer - is also having an impact on the world market, and there has been news of supply shortages on the global front. Its cost has also quadrupled during the past 11 years.

This situation of a vast and readily available market, supported by good prices, has seen many manufacturers happy to continue with their present style of business and not look further to newer markets. A lack of market information has also hindered efforts to find alternative uses to better exploit barite’s exceptional properties, such as its inertness, heaviness, radiation shielding effect, high specific gravity, non-toxicity, opacity and insolubility.

However, there have been some developments in this area, with barite manufacturers and processors from countries such as Algeria, Brazil, China, France, Gabon, Germany, India, Morocco, Netherlands, Spain, Tunisia, Turkey, UAE, the UK and the US forming associations in which either mine owners or significant barite processors meet and visit mines and processing facilities.



Properties of barite

Barite is a barium salt of sulphuric acid. Pure barite is white, opaque to transparent. It is a common mineral of greatly varying habit and a variety of parageneses in sedimentary rocks and a frequent late gangue mineral in ore veins.

It usually occurs in crystal groups (also known as crested barite), which are coarse and granular in nature and found in calcite, cerussite, dolomite, quartz, sulphur and gypsum, with a minuscule amount of strontium. Its colour varies from colourless to red, orange, yellow, white and brown. It is not as soft as talc, since its hardness varies from 2.5-3.5 (on the Mohs scale of mineral hardness) and specific gravity from 4.3 to 4.6. Its tenacity is brittle, with one perfect cleavage and two good cleavages similar to iso-structural minerals. Barite is non-toxic and inert to acids and bases, although an exception is with hot concentrated sulphuric acid. It remains highly insoluble in water, which is considered to be the lowest in the case of barite when compared with the other barium compounds.

It has a tabular, often very large crystal prismatic equi-dimensional structure - that is, rhombic bi-pyramidal - as it crystallises in an orthorhombic system. It appears in feather-like and crested groups, concretionary masses and, as with other common minerals, it is also fine-grained and rock-like. In certain instances, bladed or tabular crystals of barite form a concentric pattern of increasingly larger crystals in an outward direction. This has the appearance of a flower and when coloured red by iron stains, these formations are called desert roses (see Figure 2). Celestite (SrSO4) has the same structure as barite and forms very similar crystals. It is often an accessory mineral to other minerals and can make an attractive backdrop to brightly coloured crystals.

The mineral is widely distributed throughout the world and often occurs in veins with lead and zinc minerals. Barite has been found at locations in Brazil, Canada, Chile, China, India, Greece, Iran, Ireland, Liberia, Morocco, Peru, Romania , Turkey, South Africa, Thailand, the UK and the US. Mining in the US takes place at Arkansas, Connecticut, Virginia, North Carolina, Georgia, Tennessee, Kentucky, Nevada and Missouri.

World resources of barite have been estimated at 240m tonnes. Considerably larger deposits are found in China, which is also the world’s leading country in terms of barium sulphate mining. Major barite producers by tonnage in 2010 were: China (3.6m), India (2m), the US (670,000), Morocco (572,000), Iran (250,000), Turkey (225,000) and Kazakhstan (200,000).

A comparison of world production with respect to China and India is shown in Table 1 and Figure 3.

Barite is often an accompanying mineral in a sulphide ore vein, and is even more common in sedimentary rocks, where it forms concretionary nodules and free-growing crystals in open spaces. Veins of almost pure barite have been mined in several localities. The finest large barite crystals have come from Cumberland, UK, where single, many-faced, free-growing crystals were as long as 20cm. The UK occurrences are notable for their delicate colouring and well-formed crystals. There are many other good localities, however, such as Baia Sprie (Felsšbanya), Romania, which is associated with stibnite needles, usually in flat, colourless or yellowish crystals. Meanwhile, in Morocco and Egypt it is found in unattractive but giant 30cm-long crystals. Other global occurrences are too numerous to be included here.

In the US, it is mined in Missouri, where white-bladed masses are found where the soil came into contact with under-composed limestone and barite settled as the enclosing rock weathered away. Good white-to-clear crystals, some 30cm long, have also been found in Missouri. It is also found in perfect imitative “roses” of a red-brown colour and sandy texture near Norman, Oklahoma. Meanwhile, fine crusts of blue crystals are found in veins in soft sediments near Stoneham, Colorado, while great concretions, known as septarian nodules, found in South Dakota, contain fluorescent, transparent, amber-coloured crystals up to 10cm long in the cracks.



India - the world’s second-largest barite producer

The total barite resource in India as of early 2010 was 73m tonnes, according to the UNFC system, made up of 43% reserves and 57% remaining resources. It has been estimated that about 40% of resources are of oil-well drilling grade, followed by 6% of chemical grade, 1% paint grade and 33% of low grade. About 20% of the resources are of other, unclassified and unknown categories.

Andhra Pradesh province alone accounts for 99% of the country’s barite resources, where several important deposits are found. In the Dhone district, deposits occur in the form of numerous barite veins. The best variety is found in neighbouring Balapalapalle, and this deposit is the most productive. Other good deposits of very high-grade barites are also found in the neighbouring areas of Hussainpur, Ramapura and Janapalacheruvu.

In the Kadapa area, near Mittamidapalle village, barite bearing veins with a thickness of about 0.6 metres are found in some localities around the neighbourhood of the Tummaluru reserve forest. Good deposits of crystalline, white-variety barite occur in the Uppalapalle and Rajupalem areas. Most of the veins are found as replacements in the Vempalle limestone, and Cuddapah traps are primarily responsible for the formation of barite veins.

In the Anantapur district of Andhra Pradesh, the principal deposits occur in Nerijumapalle, Matsukota and Chandana, which are all in Tadipatri Taluk. Important barite deposits are also found in and around Mutsukota at a distance of about 5km from the village, where barite-bearing veins are more than 91.4 metres in length, with a width of 9.1 metres.

In the Khammam district of the same state, the barite veins traverse the biotite-chlorite schists and limestone of Precambrian age. The barite is associated with white chert and quartz, mostly confined to the bedding planes, and schistosity. The barite is associated with a small amount of strontium in the snow-white crystalline variety.

Most of the barite mines are controlled by the state-owned Andhra Pradesh Mineral Development Corporation (APMDC) Ltd. The corporation owns mines in Mangampet village near Kodur in Obulavaripalli in Kadapa (Cuddapah) district. Rajasthan also shows good economic deposits of barite near the Udaipur region.

In Bihar near Ranchi, in the neighbourhood of Tatisilwai, barite veins associated with galena are found. The quality is off-coloured and it is used in paints. Similar deposits are also found in Bahea, Bongaibera in Ranchi and at Kolpotka in the Singhbhum district of Bihar.

There are several deposits of barites of economic value in Madhya Pradesh state. These are at Surajpura near Chakrata hill, Orchha district (where the deposits are in considerable quantity) and Rehti in the Nemawar district of Indore. There are also several localities in Jabalpur district, where a significant amount of barite veins are known to occur.

The reserve is calculated at 20,000-30,000 tonnes of all varieties of marketable quality. Occurrences are in the form of fissure veins and lenticular pockets, replacing the dolomitic limestone of the region. It is estimated that the deposits may yield about 50,000 tonnes of different grades of barite. Barite formed in veins replacing dolomite is usually white and sub-off colour, and sometimes large and very coarsely crystalline. The BaO content is 63.17% and SO4 is 32.96%.

Another good occurrence of barite is in Orissa state, to the east of Khatanga, near the eastern border of Gangapur. The vein is about 0.9 metres occurring in mica schists. Another inferior grade of deposit is found in West Bengal, where off-colour barite is present in the Malthole village in the Purulia district.



Production

Indian barite production hit 2.33m tonnes in 2010-11, an increase of 8% compared with the previous year. This growth could not be sustained in 2011-12, however, as it fell by 26% to 1.72m tonnes. But this shortfall cannot be attributed to a decrease in demand. Andhra Pradesh continued to be the leading state for barite production, accounting for 99% of total output according to an IBM report for 2011-12. The major producing company is APMDC, which has quarries in Kadapa district of Andhra Pradesh and contributed more than 95% of the total production in India. Nominal production also came from Rajasthan.

APMDC is the sole producer in the public sector, which accounted for 98% of the total production during 2010-11 and 99.5% the following year. Almost all the barite produced was of the off-colour variety, with only nominal production reported of the snow-white variety, which mainly came from the Udaipur district of Rajasthan. Around 60% of India’s barite production is for export.

APMDC officials have confirmed that a water indentation problem occurred at one quarry, which meant ore could not be mined. There were also other labour-related problems meaning that the desired levels of production could not be achieved in 2011-12. However, the company aims to achieve about 1.9m tonnes in this financial year, ending 31 March 2013.

Other barite producing companies are Salaruddin Grey Barytes in Andhra Pradesh and Rajasthan Barytes Ltd in Rajasthan.



Consumption

India is a country of vast mineral wealth as well as a significant market in itself. As APMDC is the chief producer of this heavyweight mineral, it could be argued that production is mainly under state government control. Government policy is to supply 60% of total production for exports, with the balance going to the domestic market for sectors such as oil and gas, chemical, paints, glass, paper and so forth. The reported consumption in various industries is shown in Figure 4.

The chart data shows that the oil-well drilling industry is the largest barite consumer, accounting for 78% of consumption, followed by the chemical industry with 18%. Other barite-consuming industries such as paint, asbestos products, glass, rubber, paper and cement accounted for the remaining 4%.

Barite powder containing minimum 90% barium sulphate with 4.15 specific gravity is recommended for drilling. For offshore drilling, the specific gravity should be 4.2. At least 97% of ground barite should pass through a 75-micron IS sieve and 95% through a 53-micron IS sieve.

The major barium chemicals obtained from barite are carbonate, chloride, oxide, hydroxide, nitrate, peroxide and sulphates. Barium titanates find use in miniature electronic and communication equipment. For the chemical industry, purity is the prime criterion, with ferric oxide and strontium sulphate limited to a maximum 1% and fluorine to traces. Mesh size is also important in manufacturing chemicals. Barite used in explosive manufacture may be bleached or unbleached, and it should be in dry powder form, free from extraneous matter. Barite is also used in the paint industry and should be free from mud, clay or siliceous minerals. The presence of iron oxide is undesirable and the material should be in the form of dry powder. In glass manufacturing, iron is the most undesirable impurity.

Barite is used as a filler and extender in rubber products and material containing minimum 99.5% BaSO4 is usually preferred for this purpose. Since such purity material is not found in nature, barite is normally bleached before use and is called blanc fixe. The sieve residue through 75-micron and 150-micron sieves should be 4% and 0.01% max, respectively. BIS has prescribed IS:1683-1994 (reaffirmed 2008) as specification of barite for use in rubber industry.

Barite is used in the manufacture of asbestos products required for auto-brake lining and other frictional materials, while it is also used as a filler in paper industry. Finely ground barites and clay find application as a suspension in the Barvois system of coal washing, while it is also used in explosives and pyrotechnics composition.

Barite, like many other minerals, is also used as filler in numerous applications. It can also be substituted by diatomite, feldspar, kaolin, mica, talc and silica flour.



Uses and applications

Barite is one of the key ingredients in rat poison, giving yet another example of its use beyond that of a weighting agent in oil extractions. But it is undisputed that the mineral is predominately used in oil-well drilling applications. Its properties, such as insolubility in water, inertness and high specific gravity, enable barite to be used as a weighting agent in drilling operations to control pressure and prevent blow-out, while also providing lubrication. The American Petroleum Institute specification API 13/ISO 13500, which governs barite for drilling purposes, does not refer to any specific mineral, but rather to any material that meets that specification. In practice, this is usually barite. It is finely crushed and mixed with water to form a mixture known as thixotropic mud. The mixture is then pumped into drill stem for oil extraction. Due to the high density property of barite, the pressure exerted by the mixture on the walls of the oil well forces the release of the oil and gas from the ground.

Barite is also used as an aggregate in preparation of heavy concrete and cement for use in heavy construction equipment and for making ballasts for tractor tyres. Barite also finds use when it is mixed with cement to make special radioactive storage tanks to store radioactive materials.

Industrial uses of barite are shown in Table 2.

Blanc fixe - a form of barite

Barium sulphate is a useful white pigment particularly in its precipitated form. It is first finely crushed, acid-washed and dried or changed to blanc fixe. About 70% of the blanc fixe produced is used in coating compounds. Blanc fixe is brighter than barite and is used in primers and fillers for automobile finishing, industrial varnishes, building paints and construction coatings, wood varnishes and printing inks. In covering coats and enamels, it is used as “spacer” to improve titanium dioxide pigment scattering or to avoid flocculation of organic or inorganic coloured pigments. Compounds that consist of zinc sulphide and barium sulphate as a white pigment (lithopone) have become less important.

Special glasses are used in computer monitors and television tubes to minimise radiation effects, while barite compounds are also used in friction material on vehicle applications such as clutches and brake pads. Wollastonite is known to be a very good material here, but the use of barite is also significant. Barite is finely crushed for use as fillers in floor coverings (linoleum flooring) and in the manufacture of paper, oil cloth, rubber, cosmetics and so forth. Barite as blanc fixe serves as pigment in paints, enamels, lacquer and plastics. It is the main material in making white pigment (lithopone - a mixture of barium sulphate and zinc sulphide). This pigment is used in making white paint that produces an attractive appearance to wooden artefacts. Barite compounds are also used as catalytic agents in initiating aluminothermic reactions in welding rail tracks.

Patients who are to undergo special X-ray tests for examining colons and intestines, use barite in the form of a “Barium Milkshake”. Due to its opacity, high atomic weight and specific gravity, it can absorb gamma and X-rays completely, producing a clear picture of the organs during examination.

Barite is also known for different types of chemical uses. There are many compounds which are derived only from barite. Firstly, barium as an element is derived from barite. Other compounds are chloride, titanate, hexaferrite, hydroxide, oxide and so forth. Barium nitrates are used in ceramic glazes and fireworks. Barite is also the source of barium chloride, which softens water, while barium carbonate is used as a pottery glaze, frit and colour and also as a rat poison. Barite compounds such as fluorides are used in infra-red applications for making optics.

In cell and electronic vacuum tubes, an elemental form of barium is used to give oxygen a scavenger effect. Barite is also used as a filler or extender in cloth, ink and plastic products. Expensive white pigments get a superior whiteness by blanc fixe, which is even whiter than natural white-grade barite. It is also used to increase the surface hardness and scratch resistance of polyolefin and also to produce tint-less white films or translucent plastics. It enhances the plasticity of many types of semi-crystalline thermoplastics. Blanc fixe also improves the frictional behaviour of particular synthetic-fiber surfaces. The other uses of this unique mineral are in alloys in spark plugs, while it also acts as a deoxidising agent in the manufacture of copper.

Studies are continuing on the use of barite in the form of titanates and hexaferrite with a perovskite structure, for use in electro ceramics. Barium titanate is a common ferro-electric material with a high dielectric constant. Its use is widely accepted in the manufacture of electronic parts and components. Due to the enhancements of positive temperature coefficient of resistance properties, it is used in humidity or gas sensors. The manufacture of soluble barium salts involves treatment of the mineral (usually barite) with the relevant acid, filtration to remove insoluble impurities and crystallisation of the salt.

Barium carbonate is used in the glass industry and in the brick and clay industry. When barium carbonate is added to the clay used in making bricks, it immobilises the calcium sulphate and prevents it from migrating to the surface of the bricks and producing a whitish surface discolouration. Barium sulphate (98%) is used as a rubber reinforcing filler and for acid-proof rubber. It is insoluble in water, and this property is used when testing for the sulphate radical.

The unusually high gravity in such a light-coloured mineral is significant. Although barite contains a “heavy” metal (barium), it is not considered to be a toxic chemical by most governments because of its extreme insolubility.