They include albite (NaAlSi3O8), anorthoclase ((Na,K)AlSi3O8), sanidine ((K,Na)AlSi3O8), orthoclase (KAlSi3O8), and microcline (KAlSi3O8). Analysis revealed that it is made up almost entirely of anorthite, a plagioclase feldspar, and is approximately 4 billion years old. Feldspar can be characterised by: Note when using feldspar: depending on the particle size distribution of certain products, they can be labelled STOT RE 2. These are the main properties, uses, and facts you need to know about potassium feldspar mineral. They have glass-like luster making them a valuable resource in the jewelry industry. Feldspars are hard minerals, all of them with a hardness of 6 on the Mohs scale. Learn more about the properties and uses of feldspar in this article. Chemical weathering of feldspars results in the formation of clay minerals[19] such as illite and kaolinite. Faceted feldspar: Two specimens of labradorite feldspar that have been cut into faceted stones. (1996), Klein, Cornelis and Cornelius S. Hurlbut, Jr. Handbook of Mineralogy, Wiley, pp. Crushed and powdered feldspar are important raw materials for the manufacture of plate glass, container glass, ceramic products, paints, plastics and many other products. Alkali feldspars are grouped into two types: those containing potassium in combination with sodium, aluminum, or silicon; and those where potassium is replaced by barium. [2], Rubicline is a rare rubidium-bearing feldspar with a chemical composition of (Rb,K)(AlSi. To appreciate the importance of feldspar as a rock-forming mineral, lets consider its abundance in Earths crust. Labradorite is intergrown with microscopic layers of plagioclase minerals such as albite to produce a polished gem that scatters light in different wavelengths, resulting in iridescent reflection. In nature, many melts contain abundant sodium or calcium, along with abundant aluminum, silicon and oxygen. Pure fragments of K-feldspar crystals usually form rectangular blocks with irregular ends. There are two families: Unispar FF and Unispar PG (W). Aventurescent sunstone: Close-up photo of a sunstone cabochon, showing beautiful flashes of aventurescence caused by light reflecting from the copper platelet inclusions within the stone. Feldspars usually are white or nearly white, though they may be clear or light shades of orange or buff. The fragments within the meteorite are mostly feldspar and pyroxene. The plagioclase feldspars form a solid solution series between the end members of pure albite (NaAlSi3O8) and pure anorthite (CaAl2Si2O8). Specimens from Oregon are often called "sunstone" - even nonphenomenal specimens without the aventurescence that many people believe is needed to merit the "sunstone" name. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and glass fiber. Moonstone is a gem material that consists of microscopically thin and alternating layers of feldspar minerals of different compositions.

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