Feldspar Feldspar Feldspars (KAlSiO – NaAlSiO – CaAlSiO) are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar (see below) is known as anorthosite. Feldspars are also found in many types of sedimentary rocks. The name "feldspar" derives from the German "Feldspat", a compound of the words "Feld", "field", and "Spat", "a rock that does not contain ore". The change from
Boron group of all boron extraction in the world. The United States is second, most of its yield coming from the state of California. Aluminium, in contrast to boron, is the most abundant metal in the Earth's crust, and the third most abundant element. It composes about 8.2% (82,000 ppm) of the Earth, surpassed only by oxygen and silicon. It is like boron, however, in that it is uncommon in nature as a free element. This is due to aluminium’s tendency to attract oxygen atoms, forming several aluminium oxides. Aluminium is now known to occur in nearly as many minerals as boron,