From the Greek orthos - "right" and kalo -" I cleave" in allusion to the mineral's right angle of good cleavage. Español Orthoclase is a mineral that belongs to the family of silicate minerals called feldspar. A variety of K Feldspar A more ordered low-temperature variety of Orthoclase or partially disordered Microcline.Individual localities should be verified because the adularia structural state is nearly equally represented by microcline and orthoclase specimens. { printWin.document.close(); Location: Zarzalejo, Madrid. if (printReadyElem != null) 278.33 g/mol. Scale: 1.3 x 1.2 cm. Help on Above. Scale: 5.2x4.6x2.2 cm. } If you feel any of the content is incorrect, or if you feel we are missing vital locality information, please fill out the form below so we can update the site. The cleavage angle is about 90º. feldspars). { General. Drag2 - Resize © John Veevaert, Comments: Carlsbad twinned crystal of orthoclase. var gAutoPrint = true; // Flag for whether or not to automatically call the print function I - Data Info Our Recommended Book Selection at Amazon.com, Financial Donations and Collection Acquisitions. Dbl Clk - Start-Stop Rotation These feldspar minerals form a solid solution series between NaAlSi3O8 and KAlSi3O8. Feldspar. else The deference between the feldspars and the other silicates is that the former contain a mixture of the following chemical elements: Potassium K, Calcium Ca and Sodium Na, in addition to the usual constituents of the quartz based minerals, such as Aluminum, Al, silicon Si and oxygen O. alert("Sorry, the print ready feature is only available in modern browsers. html += headTags[0].innerHTML; I - Indicies Dispersion relatively strong. may not work well with some computers. drag2 - RMB Resize/Rotate The minerals in that series crystallize from melts that usually contain both sodium and potassium ions. Former Martín Oliete Fontela collection. Microcline and orthoclase are potassium feldspars (KAlSi3O8), usually designated Or in discussions involving their end-member composition. H - Help Screen Location: Khibiny Massif, Kola Peninsula, Russia. Feldspar - Feldspar - Chemical composition: All the rock-forming feldspars are aluminosilicate minerals with the general formula AT4O8 in which A = potassium, sodium, or calcium (Ca); and T = silicon (Si) and aluminum (Al), with a Si:Al ratio ranging from 3:1 to 1:1. Scale: Crystal size 3 x 2 cm. At the time of crystallization, these ions can substitute freely for one another in the minerals crystal structure. 2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal. if (document.getElementById != null) else function printSpecial() Orthoclase is an important mineral in the feldspar group, and the chemical formula of this mineral is KAlSi 3 O 8. Rockhounds Discussion Group on Yahoo Groups Orthoclase crystals and, Orthoclase is one of the most common minerals, and is found worldwide. CID 5359268 (Aluminum) CID 190217 (Oxide) Feldspar crystal (18×21×8.5 cm) from Jequitinhonha valley, Minas Gerais, southeastern Brazil. Comments: Striated, dark violet crystal of lorenzenite in cream-colored orthoclase. The name is from the Ancient Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Keyboard B - Bonds On/Off Keyboard Biaxial (-), a=1.518, b=1.522, g=1.523-1.524, bire=0.0050-0.0060, 2V(Calc)=52-70, 2V(Meas)=65-75. 96874XSJ39. Colorless, Greenish, Grayish yellow, White, Pink. © Copyright 1997 - 2020 Hershel Friedman and Minerals.net, all rights reserved. A - Atoms On/Off if (document.getElementsByTagName != null) var headTags = document.getElementsByTagName("head"); This appears as a green-yellow solid. Common world wide occurrences. 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 % = … alert("Could not find the printReady section in the HTML"); It is a type of potassium feldspar, also known as K-feldspar. Mineral Discussion Forum from Fabre Minerals - also available in }. If you are requesting a locality be added, please only include, White, yellow, colorless, pink, orange, light blue, light green, brown, gray. printWin.print(); Former Bally Museum collection. Only a select few localities are mentioned. Feldspars ( K Al Si 3 O 8 – Na Al Si 3 O 8 – Ca Al 2 Si 2 O 8) are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth 's continental crust by weight. Moreover, this is a type of k-feldspar or potassium feldspar. var printWin = window.open("","printSpecial", 'toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=yes,copyhistory=yes,width=350,height=350'); tourmaline). Massive - Granular - Common texture observed in granite and other igneous rock. S - Stereo { Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern. … Mouse Intrusive and extrusive igneous, and metamorphic rocks. Mindat.org's Discussion Groups printWin.document.write(html); Since it is so difficult to distinguish between Orthoclase, Sanidine, and Microcline, they may be simply called "Potassium Feldspar". Help on Above, Colville A A , Ribbe P H , American Mineralogist , 53 (1968) p.25-37, The crystal structure of an adularia and a refinement of the structure of, orthoclase, Note: Spencer B, variety adularia, GRapi = 200.97 (Gamma Ray American Petroleum Institute Units) drag1 - LMB Manipulate Structure Potassium feldspar.