Metalloid for carbon in steel casting. Of the non-metallic elements less often recognised as metalloids, selenium—in the form of ferroselenium (50–58% selenium)—is used to improve the machinability of stainless steels. All six of the elements commonly recognised as metalloids have toxic, dietary or medicinal properties. Arsenic and antimony compounds are especially toxic; boron, silicon, and possibly arsenic, are essential trace elements. Boron, silicon, arsenic, and antimony have medical applications, and germanium and tellurium are thought to have potential. Boron is used in insecticides and herbicides. It is an essential trace element. As boric acid, it has antiseptic, antifungal, and antiviral properties.
Boron the oldest leaves and black spots in barley leaves, but it can be confused with other stresses such as magnesium deficiency in other plants. Boron Boron is a chemical element with symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in the Solar system and in the Earth's crust. Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. These are mined industrially as evaporites, such as borax and kernite. The largest known boron deposits are in