Boron, although not one of the commoner elements on the Earth as a whole, exists in the form of large, easily accessible deposits of boron minerals in a number of areas, rendering it readily available. Usually, these deposits occur in dry areas and contain the element in the form of water-soluble borates. Elemental boron has few commercial applications, but the uses of boron compounds, such as borates, are many and varied. They are found in industrial processes, manufactured products and in medicine.
One of the earliest uses of boron, in the form of borates, was in pottery, where it combined with silicates to form a hard, transparent glaze. Today, one of the most important uses of boron is in the production of borosilicate glass. This type of glass is notable for undergoing very little expansion when heated. It is therefore unlikely to crack when subjected to rapid heating or cooling, and ideally suited to use in laboratory glassware and in cookware. One well-known brand of glassware is particularly associated with these applications.
Boron is an essential element for plants, and may be added in small amounts to fertilizers for use in boron-deficient areas; too much boron, however, is toxic. Its role, if any, in animals has not been clearly identified. The element enters the metabolism through ingested food, usually in the form of borates, and although there are no known cases of boron deficiency in humans, it may be required in trace amounts. A number of benefits have been claimed for boron supplements in the diet, but evidence in support of these is inconclusive.
Boron compounds have low toxicity to humans and other mammals, but are very toxic to many insects, especially ants and cockroaches. A number of commercial insecticides contain boric acid or other boron compounds. Boric acid is also widely used as an antiseptic, an eyewash and as a treatment for some yeast infections. It is a very weak acid and does not cause irritation of the skin or eyes.
Another of the uses of boron in medicine is in a cancer treatment known as Boron Neutron Capture Therapy (BNCT). The treatment involves introducing the stable isotope boron-10 into cancer cells. This boron isotope can absorb neutrons that cause it to produce an alpha particle and a lithium ion. These particles carry a lot of energy, but do not travel far; all their energy is released within the target cell, damaging it, but leaving adjacent cells unharmed. It is thus possible to destroy tumors by adding boron-10 to a compound that is absorbed more readily by cancerous cells, then bombarding the tumor with neutrons.
In industry, one of the major of the uses of boron is in abrasives and cutting tools. Two compounds of boron, boron carbide (B4C) and boron nitride (BN) are notable for their extreme hardness. Boron nitride resembles carbon in that it can have a graphite-like hexagonal form and also a diamond like structure. The hexagonal form is used in lubricants. Like carbon, it can also be made into nanotubes and nanoribbons, whose electrical, magnetic and optical properties show a lot of promise for various electronic applications.
Boron-10, because of its ability to absorb neutrons without forming radioactive isotopes, is used for shielding purposes in nuclear reactors. Neodymium magnets also contain boron. Borates are used in a number of household cleaning and laundry products to soften hard water, in fire retardants and as a green flame colorant in pyrotechnics and emergency flares.