The order of the structure improves (becomes less random) with the decreasing temperature.īig crystals of microcline from pegmatite in Gorkhi massif, Mongolia. The less regular distribution of Al in structure, the less ordered the feldspar. The order is related to randomness of the distribution of AlO 4 tetrahedrons inside the basic SiO 4 tetrahedrons network. The high feldspars are mostly monoclinic and the low feldspars are usually triclinic. They are divided into groups of the disordered (high) and the ordered (low) feldspars. Their structure is based on three dimensional network of SiO 4 tetrahedrons which are partially replaced by AlO 4 tetrahedrons.įeldspars form monoclinic or triclinic crystals. Structure and Chemical Composition of Feldsparsįeldspars belong to the tectosilicates, sometimes referred also as network silicates. Labradorite rich rocks or amazonite granites are also used as decorative building stones. Gem quality clear feldspars, moonstone and labradorite are used in jewelry. Their content in most sedimentary rocks is much less significant.įeldspars are mostly used in ceramics industry. As such, they are one of the most important mineral groups on the Earths surface: some estimate that they form between 50-60 % of the Earths crust. Feldspars are alumosilicates of alcalic metals and form a significant portion of many volcanic and metamorphic rocks.
