Feldspar is one of the most common minerals used in the ceramic and glass industries. It is an alkali-bearing aluminosilicate corresponding to the empirical formula R20, AJO3, 6SiO2, where R represents an alkali metal. As none of the feldspar group of minerals is found pure, potash feldspar always contains some soda feldspar and vice-versa with varying amounts of free quartz, iron oxide and traces of lime and magnesia resulting in a range of colors.