Alternate names are alkali feldspar, potassium feldspar an K-feldspar.The gem kent as muinstane is lairgely componed o orthoclase. Has perfect cleavage on {001} and good cleavage on {010}. Occurrence and associations : Orthoclase is common in many kinds of silicic ig-neous rocks, sediments such as arkoses, and a variety of metamorphic rocks. The name is from the Ancient Greek for "straight fracture," because its two cleavage planes are at right angles to each other. The gem known as moonstone (see below) is largely composed of orthoclase. If it shows opalescence, we call it moonstone. Orthoclase, or orthoclase feldspar (endmember formula KAlSi3O8), is an important tectosilicate mineral which forms igneous rock. Sanidine is common in rapidly cooled volcanic rocks such as obsidian and felsic pyroclastic rocks, and is notably found in trachytes of the Drachenfels, Germany. In cavities in basalts; in high-grade metamorphic rocks and as a result of potassic hydrothermal alteration; also authigenic and detrital. Your email address will not be published. The gem known as moonstone (see below) is largely composed of orthoclase. Orthoclase Meanings, Zodiacs, Planets, Elements, Colors, Chakras, and more. It is the state gem of Florida. It is a type of potassium feldspar, also known as K-feldspar. dic.academic.ru RU. Together with the other potassium feldspars, orthoclase is a common raw material for the manufacture of some glasses and some ceramics such as porcelain, and as a constituent of scouring powder. Distinguishing orthoclase from its polymorphs, microcline and sanidine, can be very difficult without X-ray or opti-cal data. It is also cut as a gemstone. It is a type of potassium feldspar, also known as K-feldspar.The gem known as moonstone (see below) is largely composed of orthoclase. Color : white, pink, turbid. It can be difficult to see cleavage in thin section due to orthoclase's low relief. General Orthoclase 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 Habit : Crystals are prismatic, stubby to elongate, and may be flattened or doubly terminated. Hand Specimen identification: The luster, hardness, and color of orthoclase are similar to other feldspars, but (in contrast with pla-gioclase) orthoclase is frequently pink or flesh col-ored, has cleavage planes that meet at 90o, and does not show twin striations.Association with other fel-sic minerals also helps identification. Orthoclase has several commercial uses. Orthoclase is one of the ten defining minerals of the Mohs scale of mineral hardness, on which it is listed as having a hardness of 6. Scientists reveal likely origin of Earth’s oldest crystals. Most moonstones are translucent and white, although grey and peach-colored varieties also occur. Orthoclase – from Greek for straight and fracture, in reference to the cleavage angle, which is 90°. Point Group: 2=m: Crystals commonly short prismatic along [100] or [001], tabular on [010], to 20 cm. A major constituent of low-temperature metamorphic rock s. Also in igneous environments such as pegmatite s, as well as sedimentary conglomerate s. Name used to describe the minerals belonging to the potassium feldspar group, specifically Orthoclase… Leave a comment It is sometimes confused with calcite or corundum but can be distinguished by its hardness. In gemology, their luster is called adularescence and is typically described as creamy or silvery white with a "billowy" quality. It is a raw material used in the production of glass, ceramic tile, porcelain, dinnerware, bathroom fixtures, and other ceramics. [5] The optical effect of adularescence in moonstone is typically due to adularia. Orthoclase is a common constituent of most granites and other felsic igneous rocks and often forms huge crystals and masses in pegmatite. [6], The largest documented single crystal of orthoclase was found in the Ural mountains in Russia. Cleavages intersect at 90°. 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. feldspar group The cleavage angle is about 90º. Hand Specimen identification: The luster, hardness, and color of orthoclase are similar to other feldspars, but (in contrast with pla-gioclase) orthoclase is frequently pink or flesh col-ored, has cleavage planes that meet at 90o, and does not show twin striations. Association with other fel-sic minerals also helps identification. [4] It was first described by Ermenegildo Pini in 1781. February 27, 2018 The common feldspar of granites, granite pegmatites, and syenites. Related Minerals : The principal K-feldspar polymorphs are sanidine (high-temperature form), orthoclase (moderate-temperature form), and microcline (low-temperature form). Several other related minerals are known: Adularia is a colorless, transparent form of K-feldspar that forms prismatic crystals. It measured ~10×10×0.4 m and weighed ~100 tons.[7]. Structure and composition : The structure of orthoclase consists of a three-dimensional framework of SiO4 and AlO4 tetrahe-dra. Biaxial, a = 1.521, b = 1.525, g = 1.528, d = 0.007, 2V = 60° to 65°. Геофизика: ортоклаз. Named "orthose" in 1801 by Rene Just Haüy from the Greek orthos - "right" in allusion to the mineral's right angle of good cleavage. Typically, the pure potassium endmember of orthoclase forms a solid solution with albite, the sodium endmember (NaAlSi3O8), of plagioclase.

orthoclase feldspar cleavage

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orthoclase feldspar cleavage 2020