SOROSILICATES. Note Carlsbad twinning. Sanidine is found most typically in felsic volcanic rocks such as obsidian, rhyolite and trachyte. Clastic sediments may also contain sanidine, but microcline and orthoclase are more common. Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. Sanidine is stable at the highest temperatures, and microcline at the lowest. Clinozoisite. KAlSi 2 O 6. The K-Feldspars include Anorthoclase, Microcline, Orthoclase, and Sanidine. KAlSiO 4 . Sanidine crystallizes in the monoclinic crystal system. Acicular in spherulites. Sanidine (K;Na)(Al;Si)4O8 °c 20 1M i nera lD t Pub sh g, v o . The crystal structure of sanidine at 935 C European Journal of Mineralogy 8 15-24: 1996: 0: 293: 0007255: Sanidine The Henkel Glossary of Fluorescent Minerals, Dr. Gerhard Henkel, Published by the FMS, 1989 , Fluorescence: Gems and Minerals Under Ultraviolet Light, Manuel Robbins, 1994, … Leucite. You can find the explanation on the alkali feldspar page. Ca 2 Al 3 Si 3 O 12 (OH) Kalsilite. Quartz SiO 2. The perthitic textures in the alkali feldspars of … CaAl 2 Si 2 O 7 (OH) 2. CYCLOSILICATES . The crystal structure of sanidine at 935 C European Journal of Mineralogy 8 15-24: 1996: 0: 293: 0006611: Sanidine: Kimata M, Shimizu M, Saito S (1996) High-temperature crystal structure of sanidine Part II. NaAlSiO 4. Sanidine is the high temperature form of potassium feldspar with a general formula K(AlSi3O8). Orthoclase, or orthoclase feldspar (endmember formula K Al Si 3 O 8), is an important tectosilicate mineral which forms igneous rock.The name is from the Ancient Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Sanidine is a member of the alkali, or potassium Feldspars (K-Feldspars) of the Feldspar Group of minerals that includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. Ca 2 Fe +3 Al 2 Si 3 O 12 (OH) Nepheline. Sanidine is the common K-feldspar in silicic volcanic rocks such as rhyolite, rhyodacite, phonolite, and trachyte, and in dikes and other shallow intrusives of the same composition. Point Group: 2=m: Crystals commonly tabular on f010g, with a square cross section, to 50 cm. Cristobalite. Sanidine is an alkali feldspar intermediate in composition between albite and orthoclase. SiO 2. H 2 O. Tridymite. Orthoclase is a monoclinic polymorph stable at low Crystal Data: Monoclinic. General Microcline Information : Chemical Formula: KAlSi3O8 : Composition: Molecular Weight = 278.33 gm Potassium 14.05 % K 16.92 % K 2 O: Aluminum 9.69 % Al 18.32 % Al 2 O 3: Silicon 30.27 % Si 64.76 % SiO 2: Oxygen 45.99 % O: 100.00 % 100.00 % = TOTAL OXIDE Lawsonite. SiO 2. The K-Feldspars include Anorthoclase, Microcline, Orthoclase and Sanidine. In thin section, alkali feldspar grains often look like they’re sprinkled with dirt (PPL) or tiny confetti (XPL). Sanidine is a member of the alkali, or potassium Feldspars (K-Feldspars) of the Feldspar Group of minerals that includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine, and Sunstone. Epidote. It is a type of potassium feldspar, also known as K-feldspar.The gem known as moonstone (see below) is largely composed of orthoclase. 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