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Only a few of the many minerals that contain boron are commercially valuable. Substances containing boron oxide are commonly known as borates. The major borate minerals being produced are borax, colemanite, datolite, kernite, probertite, szaibelyite, tincal, and ulexite. The largest deposits being mined are sedimentary rocks formed during the Cenozoic Era as a result of evaporation of geothermal springs. Major deposits occur in South America, Turkey, and the United States in the form of ores and brines. At the Kramer deposit in California and the Kirka deposit in Ankara, Turkey, open-pit mining methods are used to mine two very large deposits of high-grade beds of tincal. South American borates are primarily ulexite but deposits of tincal and howlite also are mined. In Russia, datolite, a calcium borosilicate, and szaibelyite, a magnesium borate, are mined in low-grade deposits. The UK-based company Borates PLC is developing the Satimola borates deposit in western Kazakhstan with a view to becoming a new, significant and stable source of borates for global customers. China also produces borates from low-grade deposits of brines and szaibelyite (ascharite).
The following pie chart shows world consumption of boron minerals and chemicals:
Turkey and the United States are the leading producers of borates. In 2007, Turkish production provided 35% of the world supply, based on B2O3 content, with the United States providing 29% of supply. Turkey had the highest net exports in 2007. Other countries that are significant exporters include Argentina, Chile, and Malaysia. Europe and Japan rely on imports for their boron mineral and chemical supplies. China is the world’s third-largest producer of primary boron chemicals after Turkey and the United States and is the third-largest consumer of boron chemicals after the United States and Europe. Other major boron mineral importing countries or regions are Brazil, China, and Japan. The leading boron producing companies are Rio Tinto Plc with boron mines in Argentina and the United States and Eti Holding A.S. with mines in Turkey.
In the United States and Europe, three market segments—textile glass fiber, insulation glass fiber, and enamels and glazes—may consume either boron mineral directly or derived boron chemicals as the source of B2O3. The decision to use mineral versus chemical boron is determined by the full cost associated with either alternative. For nearly twenty years, Turkey has been the major source of boron mineral for direct use in the United States and Europe.
Boron minerals will continue to offer B2O3 source cost/benefit competition to primary boron chemicals in certain market segments. However, the B2O3 source will increasingly be purchased in a ready-to-use form as chemical or mineral.
Boron compounds are used in a wide variety of products and manufacturing processes. The most important boron compounds in terms of volume are borax, boric acid, boron oxide, boron carbide, boron hydroxide, boron nitride, elemental boron and ferroboron. A growing and important use of zinc borate, ammonium pentaborate, and boric oxide is as fire retardants in the plastics industry. Zinc borate is of commercial importance because it is water insoluble and does not release water until heated to 290ºC. There are advantages in partially replacing alumina trihydrate (ATH), used as a halogen-free fire retardant in ethylene–vinyl acetate polymers, with zinc borate. Partial replacement of ATH with zinc borate results in a tenfold increase of char and changeover from the glowing to smoldering combustion mode.
Boron-doped diamond, which is normally a semiconductor, turns into a superconductor at low temperatures. The synthetic diamond containing about 3% boron becomes a superconductor at 4°K. Because it can carry electricity without resistance, superconducting diamond might be useful for making improved power storage devices or electrical motors.
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