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
Tales from the Flat Earth of agate, the second is made of blue steel, and the third gate is made of black fire. There is only one city in the Underearth – Druhim Vanashta, the city of demons. It is made of precious minerals, gems, and metals and is beautiful, though its inhabitants are cruel and wicked. The Flat Earth appears to include temperate, sub-tropical, and tropical zones, including many deserts. Since "polar" regions would be impossible on a flat world, they are not mentioned in the series. There are many seas, but bodies of water large enough to be called "oceans" do not appear