Boron ores

BORON ORES (EN: borax, tincal; DE: Borerze; FR: minerais boriques; ES: minerales boricos; RU: борные руды) are the natural mineral formations, which are containing boron within such compounds and concentrations, at which their industrial usage is technically possible, and economically feasible.

As boron ores, there are used few natural borates and borosilicates, the quantity of which increases with identification of the new endogenous deposits. Native boron belongs to the composition of borates, borosilicates, boroaluminosilicates, hydroxy-fluoroborates, and other minerals. The most distributed are the borates of sodium, calcium, and magnesium. The accompanying useful components of the boron ores are iron within the magnetite-containing ores, tin within stannoborates [nordensheldite CaSn4+(BO3)2; ludwigite and its monoclinic analogue, namely, hulsite (Fe2+Mg)2(Fe1-2x3+Snx4+Mgx)(BO3)O2], and sulfides of the non-ferrous metals, which are accompanying boron ores, or are having independent significance.

They divide the deposits of the boron ores genetically and according to mineral composition into endogenous and exogenous. Endogenous deposits have prevalently contact-metasomatic genesis, and are formed by borates within the formation of magnesial skarns, or by borosilicates within the formation of calcareous skarns. Boron ores form significant in terms of sizes sublayer, lenticular, columnar, and stockwork depositions within the exocontacts of the massifs of granitoids. The ore-containing rocks are skarns, skarnoids, zones of calciphyres and marbles. Within the magnesial skarns, and within their carbonatic border, there localize themselves the medium and large deposits of ludwigite (the average content of B2O3 is 5-8%), suanite (12-18% of B2O3), kotoite (5-10% of B2O3), and kurchatovite-sakhaite (8-15% of B2O3) ores; the largest deposits belong to the abyssal facies. Within the calcareous skarns of industrial deposits, boron ores are represented by datolite and danburite (the average content of B2O3 is 7-11%) within the skarns and skarnoids of hypabyssal facies. As boron ores, there is possible the usage of concentrations of tourmaline within the greisenized granites, secondary quartzites and veins (it acts as accompanying component within the ores of non-ferrous and rare metals). They divide the exogenous deposits of boron ores into the volcanogenic-sedimentary type, within which there prevail calcium borates (the average content of B2O3 is 20-30%), and into the halogen-sedimentary type, with magnesium borates (17-25% of B2O3). The independent type of exogenous deposits is the mineralized waters of the hot sources, the lakes of brine and of petroleum water (the average content of B2O3 is 0.1-0.7%). Exogenous boron ores form layers and lenses within sedimentary rocks and salt domes.

There is most economical the opencast method for extraction of boron ores; rich ores and complex deposits are being developed mainly by underground method. They process the beneficiated concentrates of boron ores with taking into account the properties of minerals of boron: the possibility of their decomposition by hot water, alkaline (with soda) or sulfuric acid solutions. After the preliminary decomposition of endogenous borates, there is performed the sublimation of the boric acid, which has formed itself, by superheated steam, and subsequent evaporation of water for the obtainment of boric acid in crystalline form. They conduct the beneficiation of datolite ores within neutronic separators, with subsequent flotation of datolite into concentrate (the content of B2O3 is 16%), which is subjected to decomposition by sulfuric acid, with the removal of coagulant of silicic acid by the slight drying of the slurry, and by the neutralizing of sulfuric acid with the presence of CaCO3, with the obtainment of the solution of H3BO3, from which they later evaporate water (see within the "Boron" and "Natural borates" articles about the usage of boron). They use the part of boron ores as fertilizers (for example, the ores of sakhaite type), or process them into boron-superphosphates.

The largest (up to tens of million tonnes of B2O3) deposits of endogenous borates are known within the USSR, China, North Korea, and Romania, the deposits of borosilicates are known within the USSR. Significant (up to tens or hundreds of million tonnes of B2O3) volcanogenic-sedimentary deposits of borates are located within the USA, Argentina, Peru, Chile, Turkey, and China (Tibet), while halogen-sedimentary deposits (several millions tonnes of B2O3) are located within the USSR and China. The usage of mineralized waters for the extraction of boron and other components is performed, using the brine from the Searles lake within the USA, and using the hot springs within the Tuscany province within Italy.

The explored reserves of boron ores of industrially developed capitalistic and developing countries are estimated at 72.6 million tonnes (1979), including (million tonnes): within Turkey 36.2, USA 18.1, South America (Peru, Argentina, Bolivia, and Chile) 9.1. The largest deposits of boron ores within Turkey are concentrated within the Emet (Kütahya province) and Kirk (Eskisehir province) regions. The deposits within the USA are mostly situated within the Mojave desert within the California state, and also within the Utah and Nevada states. The forecasted reserves by 2-4 times exceed the reserves, which have been explored. The extraction of boron ores amounts to more than 2770 thousand tonnes, including 1350 thousand tonnes (approximately 60%) within the USA (1981), and 1300 thousand tonnes within Turkey (1979). The extraction is also performed within Argentina (114 thousand tonnes), Chile, Peru, China, and other countries.