This article was written by Executive Consultant, Andrew Scogings.
Barite is naturally-occurring barium sulphate that is utilised primarily for its high density, in addition to chemical inertness and relative softness. Its primary use is as a weighting agent for drilling fluids in oil and gas exploration (approximately 70% of global barite consumption) while approximately 15% was used in ‘chemical’ applications in 2017, e.g. electronics, glass, ceramics and medical markets, and about 15% was used as fillers, e.g. radiation shielding in high density concrete, brake linings, rubber and paint (The Barytes Association www.barytes.org). As a general rule of thumb, higher density (SG), higher chemical purity and higher whiteness barite commands the highest prices.
Approximately 9.5 million tonnes (Mt) of barite were estimated to have been produced in 2018 and the three leading countries were China, India and Morocco, which collectively accounted for approximately 6 Mt (U.S. Geological Survey, 2019). Other significant producing countries include Kazakhstan, Mexico and USA.
World barite production essentially follows oil and gas-well drilling activity. Annual production increased from around 6 Mt in the late 1990s to peak at around 9 Mt in 2012, before declining to just over 7 Mt in 2016. Production has since recovered due to increased oil prices and hence exploration activity – reaching an estimated 9.5 Mt in 2018.
Geology and Mineralogy
Barite occurs in veins, stratiform beds and residual deposits. The largest in situ deposits currently mined are in China, India and the USA; though residual deposits contribute significantly to Chinese production (Scogings and Hughes, 2015).
Mining and Production
The geometry and type of barite deposit affect mining economics and processing complexity. Vein deposits have complex geometry and may often be extracted from surface or underground as a co-product of metals mining.
Residual deposits are shallow enough to be mined opencast using dozers, excavators or front-end loaders. Bedded barite deposits are more extensive, have more consistent grades and these can be exploited by large-scale open pit ‘hard-rock’ mining methods such as at the Mangampet mine in India, where the barite bed ranges from about 4 to 40 metres thickness.
Barite is extracted by both surface and underground mining and most barite requires upgrading to achieve minimum density or purity levels. Processing methods such as crushing and milling is often followed by wet gravity concentration methods, for example spirals and jigging to remove gangue minerals and produce correctly sized product. The jigging method uses pulsating water to separate dense barite from lower density gangue minerals such as quartz. Flotation can be used to separate barite from finely intergrown gangue minerals. Hand sorting may be used in countries where labour costs are low. Iron oxide stains can be removed using chemicals, to produce white barite suitable for coatings markets.
Barite is typically exported as crudes in bulk shipments, for milling and bagging closer to the end markets such as around the Gulf of Mexico and in the Middle East. Milled barite is packaged in bulk bags or smaller sacks on pallets.
Pure barite has a density of 4.5 g/ml, however natural barite products often contain impurities such as silicate minerals (e.g. quartz) which reduce the density.
Barite is a typical industrial mineral and is sold according to market specifications such as: density, chemical purity and particle size for oil drilling; or colour, particle size, purity and density for chemical, fillers and coatings markets.
Drilling-grade barite is specified by the American Petroleum Institute (API) and must meet certain density, chemical and sizing requirements if sold according to these specifications. Although not an API specification, drilling companies have started to focus on reducing heavy metal content, for example mercury and cadmium.
The API introduced a new low-density barite grade (density 4.10) in August 2010, in addition to the long-standing 4.20 specification. Some drillers use lower density barite around 3.9 which, although not an API specification, may be deemed to be ‘fit for purpose’ in certain applications.
The API specifies using the Le Chatelier flask method to determine the density of barite powders; however this test is slow and labour-intensive and some producers are using gas pycnometers for purposes of quality control. Gas pycnometers have a smaller laboratory ‘footprint’ and far quicker turnaround time than the Le Chatelier flask. Although the API states that “In case of dispute, the results from the Le Chatelier flask method prevail” it is hoped by some players in the industry that the gas pycnometer will eventually be specified as an accepted primary test method.
Mineral weighting alternatives to barite include celestite, calcium carbonate, ilmenite and synthetic hematite.
Reporting barite Mineral Resources and Ore Reserves
Clause 49 of the JORC Code 2012 requires that: “For minerals that are defined by a specification, the Mineral Resource or Ore Reserve estimation must be reported in terms of the mineral or minerals on which the project is to be based and must include the specification of those minerals.”
Barite is an industrial mineral and therefore ASX and NZX listed companies are required to report Mineral Resources and Ore Reserves in accordance with Clause 49 of the JORC Code.
American Petroleum Institute (2010). Specification for Drilling-Fluid Materials, API Specification 13A. Eighteenth edition, February 2010.
Scogings, A.J. and Hughes, E. (2015). Drilling grade barite. Supply, Demand & Market. Industrial Minerals Research, January 2015, 226 p.
U.S. Geological Survey (2019). Mineral commodity summaries 2019: U.S. Geological Survey, 200 p., https://doi.org/10.3133/70202434.